Answer:
60 minutes
Step-by-step explanation:
Proportions:
Number of problems done, and the time taken to finish them are in proportion.
Let the time taken to finish 40 problems = 'x'
30 : 45 = 40 : x
Product of extremes = 30 *x = 30x
Product of means = 45 * 40
Product of extremes = Product of means
30 *x = 45 * 40
[tex]\sf x = \dfrac{45*40}{30}[/tex]
x = 15 * 4
x = 60 minutes
