Question

Two cars $A$ and $B$ are moving with same speed of $45\, km/h$ along same direction. If a third car $C$ coming from the opposite direction with a speed of $36 \,km/h$ meets two cars in an interval of $5\, min$ , the distance of separation of two cars $A$ and $B$ should be (in km)

• A. 6.75
• B. 7.25
• C. 5.55
• D. 8.35

Answer 1

Answer: (A)

6.75

Answer 2

${{v}_{rel}}=45+36=81\,km/h=81\times \frac{5}{18}m/s$
${{s}_{rel}}={{v}_{rel}}\times t=81\times \frac{5}{18}\times (5\times 60)$
$=\frac{81\times 5\times 5\times 60}{18}=6750m$
$=6.75\,km$
So, the correct option is (A) : 6.75.