The procedure used to solve a problem is called Problem Solving.
Some of the problems solving strategies are: drawing a diagram, looking for the pattern, guess and check, trial and error, working forward and backward, etc.
Suppose Elisa collected 5 stamps on Monday, 10 stamps on Tuesday, and 15 stamps on Wednesday. If she continues the pattern, then, by Friday, she will be having 25 stamps, because the rule for the given pattern is 'multiples of 5' i.e. 5, 10, 15, 20, 25,...
A. 40 - 10 = 30; 5 - 2 = 3; 30 + 3 = 33
B. 40 + 10 = 50; 5 + 2 = 7; 50 + 7 = 57
C. 40 - 10 = 30; 5 - 2 = 3; 30 - 3 = 27
D. 40 - 10 = 30; 5 - 1 = 4; 30 + 4 = 34
Correct Answer: A
Step 1: Number of questions Stephen marked correct = 45 - 12
Step 2: 45 = 4 tens + 5 ones; and 12 = 1 ten + 2 ones
Step 3: 45 - 12 = (4 tens + 5 ones) - (1 ten + 2 ones) = (4 tens - 1 ten) + (5 ones - 2 ones)
Step 4: = (40 - 10) + (5 - 2) = 30 + 3 = 33
Step 5: So, the strategy '40 - 10 = 30; 5 - 2 = 3; 30 + 3 = 33' would help to solve the problem.