A man rowed 3 miles upstream in 90 minutes. If the river flowed with current of 2 miles per hour, how long did the man's return trip take?
বিকল্পসমূহ (নিজের উত্তর যাচাই করতে ক্লিক করুন):
সঠিক উত্তর
2 (30 minutes)
বিস্তারিত ব্যাখ্যা ও বিশ্লেষণ:
Solution:
Let,
the velocity of the boat be x mph
and the stream be y mph
In upstream,
In 90 minutes he goes 3 miles
In 60 minutes he goes (3 × 60) / 90 = 2 miles
ATQ,
x - y = 2
⇒ x - 2 = 2 [stream's velocity = 2 mph]
⇒ x = 4
So, velocity in downstream = x + y = 2 + 4 = 6 mph
He goes 6 miles in 1 h
He goes 3 miles in = 3/6 = (1/2 × 60) minutes = 30 minutes
