Step-by-step explanation:
The answer is in the image
The solution is in the following image
Speed=Distance/time
Here,
distance=15m
time=1sec
speed=15/1=15m/sec
Distance=Speed*time
time=15min=15*60sec=900sec
Distance travelled in 15 min=15*900=13,500m
=13500/1000 km=13.5Km
30% of 420 are first year students
first year students = (30/100 )*420
=126 students
Student who are not in first year = 420-126
=294 students
Let the father's age be x and son's be y
10 years before-
Father age=x-10
sons age=y-10
Given,
x-10=10(y-10)
x-10=10y-100
Given present age of father=40
therefore,
x=40
40-10=10y-100
10y-100=30
10y=130
y=130/10
y=13
Therefore present age of son=13years
It will provide an instant answer!