Chef's pool time initially is from 5:00 PM to 6:30 PM
So, total time for Chef to swim laps =1 hour and 30 min=1×60+30=60+30=90 minutes
Time taken by Chef to complete 1 lap =15 minutes
Therefore, number of laps that Chef can complete in the given time =total timetime taken for one lap=9015=6
Afterwards, Chef increases his time from 6:30 pm to 7:15 pm.
So, extra time for Chef =7:15−6:30
To calculate the extra time, we have to subtract the timings.
For this, we will convert the hours to minutes and do the subtraction.
7:15=(7×60)+15=420+15=435 minutes
6:30=(6×60)+30=360+30=390 minutes
Therefore, extra time in minutes =435−390=45
Chef can swim one lap in 15 minutes
So, the extra laps he can swim after increasing time
=total timetime taken for one lap=4515=3
So Chef can swim 6 laps from 5:00 pm to 6:30 pm.
On increasing time from 6:30 pm to 7:15 pm, he can swim 3 laps extra.