Question

A boat can go 3 km upstream and 5 km downstream in 55 minutes. It can also go 4 km upstream and 9 kin downstream in 1 hour 25 minutes. In how much time (in hours) will it go 43.2 km downstream?

विकल्प

• 4.4

• 3.6

• 4.8

• 5.4

Answer 1

3.6

Explanation:

`5/(x + y) + 3/(x - y)` = 55 m

`9/(x + y) + 4/(x - y)` = 1 h 25 m

(i) × 4 – (iii) × 3

`20/(x + y) - 27/(x + y)` = ( 3 h 40 m) – (4 h 15 m)

`7/(x + y)` = 35 m

Now, 7 km – 35 m

∴ 43.2 km – `(35 xx 43.2)/(60 xx 7)` = 3.6