Question

You have two candles. each burn for 60 minutes. how can you measure 45 minutes using this ?

Answer 1

since the two candles burn for 60 minutes=1hr.
after 45 minutes=45/60=3/4 hr. ..the burning candle will be 3/4 times the unburned.
mathematically it can be said as the speed of burning is inversely proportional to time.

time = height / speed
t=h(d)/s
1=1/s
therefore s = 1 unit /sec
now,

t=x/1. (where x is equal to height)
t=x=45/60=3/4