Easy Math #1

Algebra Level 2

Jimmy travels from Point A to Point B at a speed of 40 mph, then using the same road, Jimmy travels from Point B to Point A at a speed of 60 mph.

What is the average mph speed for the round trip?

40 48 60 50

Rui Chang Lu by Rui Chang Lu , 15, Oman

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3 solutions

The average speed is 2 × 40 × 60 40 + 60 = 48 \dfrac {2\times 40\times 60}{40+60}=\boxed {48} mph.

1 Helpful 1 Interesting 1 Brilliant 1 Confused

Easy and Simple explanation. Thanks!

Rui Chang Lu - 11 months, 3 weeks ago
Rui Chang Lu
Jun 24, 2020

The average speed is given by:

total distance / total time

Let x be the distance from A to B, then the total distance is equal to 2x (away and return).

The total T time is equal to time t1 = x / 40 from A to B (away) plus t2 = x / 60 from B to A (return).

Hence:

T = x / 40 + x / 60 = 100 x / 2400 = x / 24

The average speed is given by:

2x / (x/24) = 48 mph

2 Helpful 0 Interesting 0 Brilliant 0 Confused
Yichen Hu
Aug 3, 2020

I got it correct! :)

0 Helpful 0 Interesting 0 Brilliant 0 Confused

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