Answer:
1 minute should be spent on each math problem
Explanation:
Total questions = 320 
Mathematics problems = 40 
Non-mathematics problem = 320 - 40 = 280 
 
Twice the amount of time is needed for mathematics problem. 
40 x 2x + 280 x = 3 hours 
80x + 280x = 3 hours 
360x = 180 mins 
x = 0.5 mins 
2x = 0.5 x 2 = 1 min