Multiple choice

Sangram goes downstream with a boat to some destination and returns upstream to his original places in 6 hours. If the speed of the boat in the still water and then stream are 12 km/h and 5 km/h respectively, then find the distance of the destination from the starting position.

  1. 25

  2. 26.67

  3. 33

  4. 29.75

  5. 20

Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Let distance = d km. Downstream speed = 12+5 = 17 km/h. Upstream speed = 12-5 = 7 km/h. Total time = d/17 + d/7 = 6 hours. Solving: d(1/17 + 1/7) = 6, d(24/119) = 6, d = 6 × 119/24 = 29.75 km. Verification: 29.75/17 + 29.75/7 = 1.75 + 4.25 = 6 hours.