15.05.2021

Question - If the ratio of the sums of first n^th terms of two AP's is (7n + 1):(4n + 27) find the ratio of their m^th terms.

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09.07.2023, solved by verified expert
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Question - If the ratio of the sums of first, №18010166, 15.05.2021 02:49

Answer : The required ratio is (14m-6):(8m+23) .

Question - If the ratio of the sums of first, №18010166, 15.05.2021 02:49

Here we are given that the ratio of sum of first n terms of two AP's is (7n + 1):(4n + 27) .

That is.

Question - If the ratio of the sums of first, №18010166, 15.05.2021 02:49

As , we know that the sum of n terms of an AP is given by ,

Question - If the ratio of the sums of first, №18010166, 15.05.2021 02:49

Assume that ,

First term of 1st AP = a First term of 2nd AP = a'Common difference of 1st AP = dCommon difference of 2nd AP = d'

Using this we have ,

Question - If the ratio of the sums of first, №18010166, 15.05.2021 02:49

Question - If the ratio of the sums of first, №18010166, 15.05.2021 02:49

Now also we know that the nth term of an AP is given by ,

Question - If the ratio of the sums of first, №18010166, 15.05.2021 02:49

Therefore,

Question - If the ratio of the sums of first, №18010166, 15.05.2021 02:49

Question - If the ratio of the sums of first, №18010166, 15.05.2021 02:49

From equation (i) and (iii) ,

Question - If the ratio of the sums of first, №18010166, 15.05.2021 02:49

Question - If the ratio of the sums of first, №18010166, 15.05.2021 02:49

Question - If the ratio of the sums of first, №18010166, 15.05.2021 02:49

Substitute this value in equation (i) ,

Question - If the ratio of the sums of first, №18010166, 15.05.2021 02:49

Simplify,

Question - If the ratio of the sums of first, №18010166, 15.05.2021 02:49

Question - If the ratio of the sums of first, №18010166, 15.05.2021 02:49

Question - If the ratio of the sums of first, №18010166, 15.05.2021 02:49

From equation (ii) ,

Question - If the ratio of the sums of first, №18010166, 15.05.2021 02:49

Question - If the ratio of the sums of first, №18010166, 15.05.2021 02:49

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Mathematics
Step-by-step answer
P Answered by Master

\rule{200}4

Answer : The required ratio is (14m-6):(8m+23) .

\rule{200}4

Here we are given that the ratio of sum of first n terms of two AP's is (7n + 1):(4n + 27) .

That is.

\small\sf\longrightarrow \dfrac{S_1}{S_2}=\dfrac{7n +1}{4n +27}  \\

As , we know that the sum of n terms of an AP is given by ,

\small\sf\longrightarrow \pink{ S_n =\dfrac{n}{2}[2a +(n-1)d]} \\

Assume that ,

First term of 1st AP = a First term of 2nd AP = a'Common difference of 1st AP = dCommon difference of 2nd AP = d'

Using this we have ,

\small\sf\longrightarrow \dfrac{S_1}{S_2}=\dfrac{\dfrac{n}{2}[2a + (n-1)d]}{\dfrac{n}{2}[2a' +(n-1)d'] } \\

\small\sf\longrightarrow \dfrac{7n+1}{4n+27}=\dfrac{2a + (n -1)d}{2a' + (n -1)d' } . . . . . (i) \\

Now also we know that the nth term of an AP is given by ,

\longrightarrow\sf\small \pink{ T_n = a + (n-1)d}\\

Therefore,

\longrightarrow\sf\small \dfrac{T_{m_1}}{T_{m_2}}= \dfrac{ a + (n-1)d }{a'+(n-1)d'}. . . . . (ii)\\

\longrightarrow\sf\small \dfrac{T_1}{T_2}=\dfrac{2a + (2n-2)d}{2a'+(2n-2)d'} . . . . . (iii)\\

From equation (i) and (iii) ,

\longrightarrow\sf\small n-1 = 2m-2\\

\longrightarrow\sf\small n = 2m -2+1 \\

\longrightarrow\sf\small n = 2m -1 \\

Substitute this value in equation (i) ,

\longrightarrow \sf\small \dfrac{2a+ (2m-1-1)d}{2a' +(2m-1-1)d'}=\dfrac{7(2m-1)+1}{4(2m-1) +27}\\

Simplify,

\longrightarrow\sf\small \dfrac{ 2a + (2m-2)d}{2a' +(2m-2)d'}=\dfrac{14m-7+1}{8m-4+27}\\

\longrightarrow\sf\small \dfrac{2[a + (m-1)d]}{2[a' + (m-1)d']}=\dfrac{ 14m-6}{8m+23}\\

\longrightarrow\sf\small \dfrac{[a + (m-1)d]}{[a' + (m-1)d']}=\dfrac{ 14m-6}{8m+23}\\

From equation (ii) ,

\longrightarrow\sf\small \underline{\underline{\blue{ \dfrac{T_{m_1}}{T_{m_2}}=\dfrac{ 14m-6}{8m+23}}}}\\

\rule{200}4

Mathematics
Step-by-step answer
P Answered by PhD

SI=(P*R*T)/100

P=2000

R=1.5

T=6

SI=(2000*1.5*6)/100

=(2000*9)/100

=180

Neil will earn interest of 180

Mathematics
Step-by-step answer
P Answered by PhD
Answer: 440 grams for 1.54 is the better value
Explanation:
Take the price and divide by the number of grams
1.54 / 440 =0.0035 per gram
1.26 / 340 =0.003705882 per gram
0.0035 per gram < 0.003705882 per gram
Mathematics
Step-by-step answer
P Answered by PhD

For 1 flavor there are 9 topping

Therefore, for 5 different flavors there will be 5*9 choices

No of choices= 5*9

=45 

Mathematics
Step-by-step answer
P Answered by PhD
The answer is in the image 

The answer is in the image 

Mathematics
Step-by-step answer
P Answered by PhD

The solution is given in the image below

The solution is given in the image below
Mathematics
Step-by-step answer
P Answered by PhD

The wood before starting =12 feet

Left wood=6 feet

Wood used till now=12-6=6 feet

Picture frame built till now= 6/(3/4)

=8 pieces

Therefore, till now 8 pieces have been made.

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