Hello James,
We Know:
He took 40 minutes to complete 15 problems.
Find:
How much time it took him to complete 45 problems.
Solution:
45 / 15 = 3
3 sets of 40 minutes...
40 x 3 = 120
Answer:
He took 120 minutes (2 hours) to complete 45 problems!
Hope This Helps!
If you need anything else let me know!