M4maths
Maths Puzzle
Numerical Ability
Time Distance and Speed
In a kilometer race, if A gives B a 40 m start, A wins by 19 s. But if A gives B a 30 s start, B wins by 40 m. Find the time taken by B to run 5,000 m?
a. 150 s
b. 450 s
c. 750 s
d. 825 s
Read Solution (Total 1)
-
- A gives B a 40metre start then B runs 960m in T secs and A runs 1000m in T-19 secs.
2.A gives B a 30 second start then B runs 1000m in t secs and A runs 960m in (t-30) secs.
Assuming speed of A=X and B=Y
Then
X = 960 ÷ T = 1000 ÷ t,
960t = 1000T
Y = 1000 ÷ (T - 19) = 960 ÷ (t - 30)
1000t - 30000 = 960T - 18240
Then 40t = -40T + 11760,
t = -T + 294.
Substituting for t in 960t = 1000T gives
-960T + 282240 = 1000T
1960T = 282240
T = 144
B 's speed is 960 ÷ T = 960 ÷ 144 = 6.67 metres per second.
to run 5000 metres the time taken is 5000 ÷ 6.67 = 750 seconds = 12 minutes 30 seconds - 10 years agoHelpfull: Yes(2) No(3)
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