Puzzle: 209                                                                                                                 11.07.2018

Mohan and Kumar race each other in a 100m race. Mohan wins by 10m. They decide to race again, but to make thing fair, Mohan starts 10m behind Kumar making the distance for Mohan as 110m. If they both run exactly the same speed as before, who will win the race?

The answer for puzzle-208: 15 days

Solution for puzzle-208:

Let the amount spent on each day be x

and the no.of days stayed be d.

xd=42000 ----(1)

If the amount spent is Rs.700 less, the no.of days stayed will be 5 more.

(x-700) (d+5) = xd

xd – 700d +5x – 3500=xd

5x – 700d – 3500=0

X-140d-700=0

But x=42000/d

42000/d – 140d – 700=0

42000 – 140 d² – 700d = 0

140d² + 700d-42000=0

d² + 5d – 300 = 0

d² + 20d – 15d – 300 =0

d(d+20) – 15(d+20)

(d+20) (d-15)=0

d=-20 or 15 ;     d can be only 15

Since x=42000/d = 42000/15 = 2800

So the no.of days he stayed is 15 and the amount he spent is Rs.2800

If he spent Rs.700 less means, the amount spent will be Rs.2100 and the no.of days he stayed will be 42000/2100 = 20 days which is 5 more days than 15.