21.01.2023

What's 4 x 90 divided by 3 x 7?

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Step-by-step answer

24.06.2023, solved by verified expert

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Mathematics
Step-by-step answer
P Answered by PhD

(4 × 90) ÷ (3 × 7)

= 360 ÷ 21

= 17.14

Mathematics
Step-by-step answer
P Answered by PhD
1. A. According to the expression a_n=4*a_n-1, each term after a1 is four times the previous term. The first term is -7 as given, 2nd term should be -7*4=-28, 3rd term is -28*4=-112, ... A is the correct answer. 

2. B. The sequence is -13, -8, -3, 2... It's obvious that each term is equal to the previous term plus 5. This is an arithmetic sequence with initial term -13 and common difference 5. We know a1=-13, so a_n=-13+5*(n-1). The answer is B.

3. A. We are given a15=-53, a16=-5. The common difference of the arithmetic sequence is -5-(-53)=48. The formula for a_n term is a1+48*(n-1). We know that a15=-13; plug in n=15, a15=-53=a1+48*(15-1), a1=-725. So a_n=-725+48*(n-1).

4. Diverge. We are given a few terms, 11, 44, 176, 704... Observe that each term is four times the previous one. 11*4=44, 44*4=176, 176*4=704... This is a geometric series with common ratio>1. You can keep multiplying by 4 and the series goes to infinity, so it diverges.

5. D. We have -4, -16, -64, -256... Same as above, each term is four times the previous one. The initial term is a1=-4. The common ratio d=4. So a_n=a1*d^(n-1)=-4*4^(n-1)=-4^n. (D).

6. The answer is A. a2=-2, a5=16. Suppose the common ratio is D. a_n=a1*d^(n-1). a2=a1*d; a5=a1*d^4. Plug in a2 and a5: -2=a1*d, 16=a1*d^4. 16/-2=d^3=-8, d=-2, a1=1. So a_n=1*(-2)^(n-1).

7. B. We are given the sequence 4, -24, 144,... Each term is -6 times the previous one. The first term a0=4, the n^th term a_(n-1) is a1*d^n=4*(-6)^n. To express the sum, we simply have to use the sigma notation and sum 4*(-6)^n from n=0 to infinity. The answer is B.

8. D. We are given -3 + 6 + 15 + 24... 132. Each term is equal to the previous one plus 9. First term a0=-3, n^th term a_n-1 is -3+9*n. The last term is 132. 132 =-3+9n, n=15. So we have to sum -3+9n from n=0 to n=15.

9. B. 343 + 512 + 729 + 1000+...  343=7^3, 512=8^3, 729=9^3, 1000=10^3. This is a sequence of perfect cubes. Therefore, the sum is n^3 from n=7 to infinity. (The initial term is 343=7^3).

10. B. We are given 3, 5, 7, 9, ... 21. The common difference is 2. There are (21-3)/2+1=10  terms. The initial term a1=3, and last term is a10=21. The sum is (a1+a10)*10/2=(3+21)*10/2=120.

11. C. 4/3, 16/3, 64/3, 256/3, 1024/3.  Each term is four times the previous one. This is a geometric series with initial term a1=4/3 and common ratio r=4. 1024/3 is the 5th term of the sequence. So sum=a1*(1-r^n)/(1-r)=4/3*(1-4^5)/(1-4)=-4/9*-1023=1364/3.

12. B. 10,12,14,... This is an arithmetic sequence. a1=10, and common difference d=2. There are 20 terms (20 rows). a20=a1+d*(n-1)=10+2*(20-1)=48. So the sum S=(a1+an)*n/2=(10+48)*20/2=580.

13. 10 + 20 + 30 + ... + 10n = 5n(n + 1). When n=1, this expression is true, since 10=5*1*(1+1). Suppose when n=k, this statement is true, then when n=k+1, the left side is 10+...+10n+10(n+1), the right side is 5(n+1)(n+2). The left side adds 10(n+1) compared to the previous one. The right side adds 5(n+1)(n+2)-5n(n+1)=5(n+1)(n+2-n)=10(n+1). So the statement holds true.

14. The height at week 0 is a0=300 (initial height). Common difference is 4.2 (weekly increment). a_n=300+4.2n. At week n, the height of the tree is 300+4.2*n centimeters.
Mathematics
Step-by-step answer
P Answered by PhD
1. A. According to the expression a_n=4*a_n-1, each term after a1 is four times the previous term. The first term is -7 as given, 2nd term should be -7*4=-28, 3rd term is -28*4=-112, ... A is the correct answer. 

2. B. The sequence is -13, -8, -3, 2... It's obvious that each term is equal to the previous term plus 5. This is an arithmetic sequence with initial term -13 and common difference 5. We know a1=-13, so a_n=-13+5*(n-1). The answer is B.

3. A. We are given a15=-53, a16=-5. The common difference of the arithmetic sequence is -5-(-53)=48. The formula for a_n term is a1+48*(n-1). We know that a15=-13; plug in n=15, a15=-53=a1+48*(15-1), a1=-725. So a_n=-725+48*(n-1).

4. Diverge. We are given a few terms, 11, 44, 176, 704... Observe that each term is four times the previous one. 11*4=44, 44*4=176, 176*4=704... This is a geometric series with common ratio>1. You can keep multiplying by 4 and the series goes to infinity, so it diverges.

5. D. We have -4, -16, -64, -256... Same as above, each term is four times the previous one. The initial term is a1=-4. The common ratio d=4. So a_n=a1*d^(n-1)=-4*4^(n-1)=-4^n. (D).

6. The answer is A. a2=-2, a5=16. Suppose the common ratio is D. a_n=a1*d^(n-1). a2=a1*d; a5=a1*d^4. Plug in a2 and a5: -2=a1*d, 16=a1*d^4. 16/-2=d^3=-8, d=-2, a1=1. So a_n=1*(-2)^(n-1).

7. B. We are given the sequence 4, -24, 144,... Each term is -6 times the previous one. The first term a0=4, the n^th term a_(n-1) is a1*d^n=4*(-6)^n. To express the sum, we simply have to use the sigma notation and sum 4*(-6)^n from n=0 to infinity. The answer is B.

8. D. We are given -3 + 6 + 15 + 24... 132. Each term is equal to the previous one plus 9. First term a0=-3, n^th term a_n-1 is -3+9*n. The last term is 132. 132 =-3+9n, n=15. So we have to sum -3+9n from n=0 to n=15.

9. B. 343 + 512 + 729 + 1000+...  343=7^3, 512=8^3, 729=9^3, 1000=10^3. This is a sequence of perfect cubes. Therefore, the sum is n^3 from n=7 to infinity. (The initial term is 343=7^3).

10. B. We are given 3, 5, 7, 9, ... 21. The common difference is 2. There are (21-3)/2+1=10  terms. The initial term a1=3, and last term is a10=21. The sum is (a1+a10)*10/2=(3+21)*10/2=120.

11. C. 4/3, 16/3, 64/3, 256/3, 1024/3.  Each term is four times the previous one. This is a geometric series with initial term a1=4/3 and common ratio r=4. 1024/3 is the 5th term of the sequence. So sum=a1*(1-r^n)/(1-r)=4/3*(1-4^5)/(1-4)=-4/9*-1023=1364/3.

12. B. 10,12,14,... This is an arithmetic sequence. a1=10, and common difference d=2. There are 20 terms (20 rows). a20=a1+d*(n-1)=10+2*(20-1)=48. So the sum S=(a1+an)*n/2=(10+48)*20/2=580.

13. 10 + 20 + 30 + ... + 10n = 5n(n + 1). When n=1, this expression is true, since 10=5*1*(1+1). Suppose when n=k, this statement is true, then when n=k+1, the left side is 10+...+10n+10(n+1), the right side is 5(n+1)(n+2). The left side adds 10(n+1) compared to the previous one. The right side adds 5(n+1)(n+2)-5n(n+1)=5(n+1)(n+2-n)=10(n+1). So the statement holds true.

14. The height at week 0 is a0=300 (initial height). Common difference is 4.2 (weekly increment). a_n=300+4.2n. At week n, the height of the tree is 300+4.2*n centimeters.
Mathematics
Step-by-step answer
P Answered by PhD
Which is bigger 6.6 or 0.78 ?
6.6 is bigger

x^2 - xwhen x = 2
2^2 - 2 =
4 - 2 =
2 <==

A = bh
60 = 10h
60/10 = h
6 = hso height is 6 m

900 decreased by 5% =
900 - 0.05(900) = 900 - 45 = 855 <==

2(x + 3) = 8
2x + 6 = 8
2x = 8 - 6
2x = 2
x = 2/2
x = 1 <==

360 in a ratio of 1 to 4

1:4added = 5

1/5(360) = 360/5 = 72
4/5(360) = 1440/5 = 288

ratio is 72:288

3,8,13,16,23this is an arithmetic sequence with a common difference of 5

the nth term : an = a1 + (n - 1)d
an = 3 + 5(n-1) <===

are there decimals in this problembecause the angles of a quadrilateral , when added = 360 degrees

75% = 66what is full cost...
75% of what is 66..
0.75x = 66
x = 66 / 0.75
x = 88 <==

y = 4x - 1...when x = -2
y = 4(-2) - 1
y = -8 - 1
y = -9 <==

6.5 cant see the problem

circumference of circle with radius of 4
C = 2(pi)r
C = 2(3.14)(4)
C = 25.12 cm <== or C = 8*(pi)

6 km / h for 2 hrs 20 min...

6 / 60 = 0.1 km per minute0.1(140) = 14 km <==

to increase an amount by 4.6%, ur multiplier would be 1.046

(x - 5)(x + 4) =
x^2 + 4x - 5x - 20 =
x^2 - x - 20 <===

500 increased by 4.6%
500(1.046) = 523 <==

2x > 7
x > 7/2 or x > 3.5

500 tickets are soldprobability of winning first prize (if there is only 1 first prize) is 1/500dont know how many tickets he bought

6 * 0.6 = 3.6u simply multiply 6 * 6 = 36and since 0.6 has a decimal 1 space to the left, in ur answer(36)...move the decimal 1 space to the left giving u 3.6

5x - 2ywhen x = -2, y = -3
5(-2) - 2(-3) =
-10 + 6 =
-4 <==

0.521 to one significant figure = 0.5

4,7,13,22,34
4 to 7 = 3 spaces
7 to 13 = 5 spaces
13 to 22 = 9 spaces
22 to 34 = 12 spaces
I am sorryI do not know this one..cannot find the pattern

V= bh
V = 3*10
V = 30
not sure about this...because volume of a prism is base * heightthere is o (pi) in the formula.

7.34 * 4.71 = 34.5714 rounds to 34.57
5.63 + 11.89 = 17.52

y = x^2 + 2xx = -2
y = -2^2 + 2(-2)
y = 4 - 4
y = 0 <==
Mathematics
Step-by-step answer
P Answered by PhD
Which is bigger 6.6 or 0.78 ?
6.6 is bigger

x^2 - xwhen x = 2
2^2 - 2 =
4 - 2 =
2 <==

A = bh
60 = 10h
60/10 = h
6 = hso height is 6 m

900 decreased by 5% =
900 - 0.05(900) = 900 - 45 = 855 <==

2(x + 3) = 8
2x + 6 = 8
2x = 8 - 6
2x = 2
x = 2/2
x = 1 <==

360 in a ratio of 1 to 4

1:4added = 5

1/5(360) = 360/5 = 72
4/5(360) = 1440/5 = 288

ratio is 72:288

3,8,13,16,23this is an arithmetic sequence with a common difference of 5

the nth term : an = a1 + (n - 1)d
an = 3 + 5(n-1) <===

are there decimals in this problembecause the angles of a quadrilateral , when added = 360 degrees

75% = 66what is full cost...
75% of what is 66..
0.75x = 66
x = 66 / 0.75
x = 88 <==

y = 4x - 1...when x = -2
y = 4(-2) - 1
y = -8 - 1
y = -9 <==

6.5 cant see the problem

circumference of circle with radius of 4
C = 2(pi)r
C = 2(3.14)(4)
C = 25.12 cm <== or C = 8*(pi)

6 km / h for 2 hrs 20 min...

6 / 60 = 0.1 km per minute0.1(140) = 14 km <==

to increase an amount by 4.6%, ur multiplier would be 1.046

(x - 5)(x + 4) =
x^2 + 4x - 5x - 20 =
x^2 - x - 20 <===

500 increased by 4.6%
500(1.046) = 523 <==

2x > 7
x > 7/2 or x > 3.5

500 tickets are soldprobability of winning first prize (if there is only 1 first prize) is 1/500dont know how many tickets he bought

6 * 0.6 = 3.6u simply multiply 6 * 6 = 36and since 0.6 has a decimal 1 space to the left, in ur answer(36)...move the decimal 1 space to the left giving u 3.6

5x - 2ywhen x = -2, y = -3
5(-2) - 2(-3) =
-10 + 6 =
-4 <==

0.521 to one significant figure = 0.5

4,7,13,22,34
4 to 7 = 3 spaces
7 to 13 = 5 spaces
13 to 22 = 9 spaces
22 to 34 = 12 spaces
I am sorryI do not know this one..cannot find the pattern

V= bh
V = 3*10
V = 30
not sure about this...because volume of a prism is base * heightthere is o (pi) in the formula.

7.34 * 4.71 = 34.5714 rounds to 34.57
5.63 + 11.89 = 17.52

y = x^2 + 2xx = -2
y = -2^2 + 2(-2)
y = 4 - 4
y = 0 <==
Mathematics
Step-by-step answer
P Answered by Specialist
1) 5r*7/15 = 35r/15 = 7r/3
2) 1.2 (w + u/12) = 1.2w + 0.1u
3) 0.2w/2 = 0.1w
4) x +3x/4 + 0.9z = 1.75x + 0.9z
5) 4*( 3y/8  - x/2) = 1.5y -2x
6) 0.6* (  4w/6 - 5v/18 ) = 2w/5 - 5v/3 
Mathematics
Step-by-step answer
P Answered by Specialist
1) 5r*7/15 = 35r/15 = 7r/3
2) 1.2 (w + u/12) = 1.2w + 0.1u
3) 0.2w/2 = 0.1w
4) x +3x/4 + 0.9z = 1.75x + 0.9z
5) 4*( 3y/8  - x/2) = 1.5y -2x
6) 0.6* (  4w/6 - 5v/18 ) = 2w/5 - 5v/3 
Mathematics
Step-by-step answer
P Answered by Specialist

(4)and (7)

Step-by-step explanation:

A parabola has a focus of F(2,8.5) and a directrix of y=9.5. The point P(x,y) represents any point on the parabola, while D(x,9.5) represents any point on the directrix.

Now, Step 1: FP=DP, using the distance formula,

Step 2: \sqrt{(y-8.5)^{2}+(x-2)^{2}}=\sqrt{(y-9.5)^{2}+(x-x)^{2}}

Step 3: Solving the step 2,we get

\sqrt{(y-8.5)^{2}+(x-2)^{2}}=\sqrt{(y-9.5)^{2} }

Squaring on both sides and then solving, we get

x^{2}-4x+4+y^{2}-17y+72.25=y^{2}-19y+90.25

Step 4: x^{2}-4x-14=-2y

Step 5: Finding the value of y by dividing both sides by -2, we get

\frac{x^{2}-4x-14}{-2}=y

Thus, Step 4 and 5 is incorrect because she added the y-terms incorrectly and  also the previous step is incorrect on step 4.

Mathematics
Step-by-step answer
P Answered by Specialist

(4)and (7)

Step-by-step explanation:

A parabola has a focus of F(2,8.5) and a directrix of y=9.5. The point P(x,y) represents any point on the parabola, while D(x,9.5) represents any point on the directrix.

Now, Step 1: FP=DP, using the distance formula,

Step 2: \sqrt{(y-8.5)^{2}+(x-2)^{2}}=\sqrt{(y-9.5)^{2}+(x-x)^{2}}

Step 3: Solving the step 2,we get

\sqrt{(y-8.5)^{2}+(x-2)^{2}}=\sqrt{(y-9.5)^{2} }

Squaring on both sides and then solving, we get

x^{2}-4x+4+y^{2}-17y+72.25=y^{2}-19y+90.25

Step 4: x^{2}-4x-14=-2y

Step 5: Finding the value of y by dividing both sides by -2, we get

\frac{x^{2}-4x-14}{-2}=y

Thus, Step 4 and 5 is incorrect because she added the y-terms incorrectly and  also the previous step is incorrect on step 4.

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