1.

Amit travels 30 minutes at the speed of 25km/hr. Further he travles 20 minutes at the speed of 40km/hr. Find his average speed.

Answer»

25km/hr
30km/hr
31km/hr
none of these

Solution :
Since the actual ratio is 3:2 so reverse it , i.e., the required ratio is 2:3. Now DIVIDE the difference of both the SPEEDS i.e., 25 and 40 in the ratio of 2:3
i.e., `(40-25)xx2/5 = 6 and (40-25)xx3/5 = 9`
So, the avrerage speed is 25+6 = 31, or 40-9 = 31


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