What I would first do here is try to find the value of 10% relative to the 12 minutes. If we find what 10% is we can multiply that to get 100% to find the total amount of minutes he wants to study. We can then subtract the time already studied to find our answer.

To do this we want to take the 40% we have and find 10. We can do 40/4 to find this since 40 divided by 4 is actually 10.

But if we do this we also have to do with to the number it is relating to / representing. Which is 12. (12 minutes = 40%)

So we can do :

40 / 4

10%

Also

12 / 4

So with this we can conclude that 10% of his total time is 3 minutes.

Now lets multiply this by 10 to get the 100% we are looking for so we can get the total amount of time he spent studying.

So :

10% x 10

100%

3 x 10

30 minutes

So his total time is 30 minutes of studying, but we have to find how many more minutes after his 12.

We can now simply take the total time and take off the time spent already to find this answer :

30 - 12

18 minutes

That is your answer, he needs to study 18 more minutes.

I hope this helps!

If you have any questions or concerns please comment or message me! :)

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2 years ago