CAMANISHPARMAR wrote:

Thomas was riding his bike at a constant rate to the store, which is 60 miles away. If Thomas had ridden his bike 2 miles per hour faster than he actually did, he would have saved one hour. How fast did he actually ride to the store?

A) 8 mph

B) 10 mph

C) 12 mph

D) 15 mph

E) 18 mph

Ways to do it..

i) choices

since speed,s, and s+2 leave a difference of 1 hour, both should divide 60 evenly and leave a difference 1..

A) 8 mph

8 does not divide evenly into 60 but 8+2 does....eliminate

B) 10 mph

Both 10 and 12 divide evenly in to 60, and difference is 60/10-60/12=6-5=1..YES

C) 12 mph

12+2 does not divide evenly into 60 but 12 does....eliminate

D) 15 mph

15+2 does not divide evenly into 60 but 15 does....eliminate

E) 18 mph

18 does not divide evenly into 60 but 18+2 does....eliminate

so B

II) algebraic

time taken at s speed = \(\frac{60}{s}\)

time taken at s+2 speed = \(\frac{60}{s+2}\)

so \(\frac{60}{s}-\frac{60}{s+2}=1.......60s+120-60s=s^2+2s......s^2+2s-120+0.......(s+12)(s-10)=0\)

so s = -12 or 10 but s cannot be negative so s=10

B

_________________

1) Absolute modulus : http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372

2)Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html

3) effects of arithmetic operations : https://gmatclub.com/forum/effects-of-arithmetic-operations-on-fractions-269413.html

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