0.18 l ÷ 0.01 l = 18

Ali has to take the cough medicine 18 times.

One day has 24 hours.

Ali takes 24 ÷ 4 = 6 times a day.
18 ÷ 6 = 3

So Ali takes all the doses within 3 days.

Let the first timing he takes a dose be 12am (first day starts)

2nd timing : 4am
3rd timing : 8am
4th timing : 12pm
5th timing : 4pm
6th timing : 8pm
7th timing : 12am (2nd day starts)
8th timing : 4am
9th timing : 8am
10th timing : 12pm
11th timing : 4pm
12th timing : 8pm
13th timing : 12am (3rd day starts)
14th timing : 4am
15th timing : 8am
16th timing : 12pm
17th timing : 4pm
18th timing : 8pm (last dose)


So on the third day, he will finish his last dose at 8pm.

Notice that when he finished at 8pm on the 3rd day, there are still 4 hours before the end of the day.

4 hours = 1/6 x 24 hours
= 1/6 days

So we need to minus 1/6 days from 3 days


So the number of days needed
= 3 - 1/6 = 2 5/6 days

thank you!!

Welcome!

but I don't get the last statement

Basically it means Ali didn't spend 3 full days to finish the medicine.

He finished his medicine at 8pm, but there are still 4 hours before it is 12am, where the 3rd day is over and the 4th day begins.

So we cannot say Ali used 3 full days to finish the medicine.

We have subtract 4 hours = 1/6 day

ohh thank you!!