Solving Mental Math Problems
Mental math practice comprises arithmetical calculations using only the human brain, with no help from calculators, computers, or pen and paper. People use mental math when computing tools are not available, when it is faster than other means of calculation or in a competition context. Mental math often involves the use of specific techniques devised for specific types of problems. Source: Wikipedia.
Solving Mental Math Problems - Example Problems
Solving example problems
Example 1: Linda has $74 and Lisa has $99. How much did they has altogether?
Solution:
We have to add 74 and 99 to know the sum.
Step 1: Add the two ones' place digits: 9 + 4 = 13.
Step 2: Add the two tens' place digits: 9 + 7 = 16.
Step 3: The sum of the ones' place digits is a two-digit number so decrease the ones' place sum by 10: 13 - 10 = 3 and increase the tens' place sum by 1: 16 + 1 = 17.
Step 4: Combine the tens' and ones' place sums.
Answer is $173.
Example 2: A pair of shoes cost is $57. A pant cost is $81. Find the difference between the pair of shoes and pant.
Solution:
We have to subtract 57 from 81 to know the difference.
Step 1: Subtract the two tens' place digits: 8 - 5 = 3
Step 2: Bottom ones' digit is larger than the top ones' digit.
Decrease the answer for the tens' place by 1: 3 - 1 = 2 and increase the top ones' place value by 10: 1 + 10 = 11.
Step 3: Subtract the two ones' place values: 11 - 7 = 4
Step 4: Combine the tens' and ones' place value.
Answer is $24.
Example 3: A bucket cost is $73, oven cost is 5 times more than bucket cost. What is the oven cost?
Solution:
We have to multiply 73 by 5 to know the computer cost.
Step 1: Multiply the ones' digit by 5, 5 x 3 = 15
Step 2: Multiply the tens' digit by 5, 5 x 7 = 35
Step 3: Product of ones' place is two digits (15), so increase the product of tens' digit by 1 (15), 35 + 1 = 36
Step 4: Combine the ones' and twos' place value
Answer is $365.
Example 4: Lisa had 72 candies. She gave 6 candies to each her friend. How many friends she had?
Solution:
We have to divide 72 by 6 to know the answer.
Step 1: Divide the tens' digit by 6, 7/6 = 1 with remainder 1
Step 2: Multiply remainder 1 by 10, 1 x 10 = 10 and add it to ones' place, 10 + 2 = 12
Step 3: Divide 12 by 6, 12/6 = 2
Step 4: Combine the ones' and twos' place values
Answer is 12.
Solving Mental Math Problems - Practice Problems
Solving practice problems
Problem 1: Shan saved $73 and Sham saved $78. How much did they save altogether?
Problem 2: A shirt cost is $73, Pant cost is $99. Find the cost of difference of two items.
Problem 3: A wall clock costs 3 times as much as a watch. If the watch costs $51, what is the cost of wall clock?
Problem 4: Pond had 75 candies. He put the candies equally into 5 bags. How many candies were there in each bag?
Answer: 1) $151 2) $26 3) $153 4) 15
Mental math practice comprises arithmetical calculations using only the human brain, with no help from calculators, computers, or pen and paper. People use mental math when computing tools are not available, when it is faster than other means of calculation or in a competition context. Mental math often involves the use of specific techniques devised for specific types of problems. Source: Wikipedia.
Solving Mental Math Problems - Example Problems
Solving example problems
Example 1: Linda has $74 and Lisa has $99. How much did they has altogether?
Solution:
We have to add 74 and 99 to know the sum.
Step 1: Add the two ones' place digits: 9 + 4 = 13.
Step 2: Add the two tens' place digits: 9 + 7 = 16.
Step 3: The sum of the ones' place digits is a two-digit number so decrease the ones' place sum by 10: 13 - 10 = 3 and increase the tens' place sum by 1: 16 + 1 = 17.
Step 4: Combine the tens' and ones' place sums.
Answer is $173.
Example 2: A pair of shoes cost is $57. A pant cost is $81. Find the difference between the pair of shoes and pant.
Solution:
We have to subtract 57 from 81 to know the difference.
Step 1: Subtract the two tens' place digits: 8 - 5 = 3
Step 2: Bottom ones' digit is larger than the top ones' digit.
Decrease the answer for the tens' place by 1: 3 - 1 = 2 and increase the top ones' place value by 10: 1 + 10 = 11.
Step 3: Subtract the two ones' place values: 11 - 7 = 4
Step 4: Combine the tens' and ones' place value.
Answer is $24.
Example 3: A bucket cost is $73, oven cost is 5 times more than bucket cost. What is the oven cost?
Solution:
We have to multiply 73 by 5 to know the computer cost.
Step 1: Multiply the ones' digit by 5, 5 x 3 = 15
Step 2: Multiply the tens' digit by 5, 5 x 7 = 35
Step 3: Product of ones' place is two digits (15), so increase the product of tens' digit by 1 (15), 35 + 1 = 36
Step 4: Combine the ones' and twos' place value
Answer is $365.
Example 4: Lisa had 72 candies. She gave 6 candies to each her friend. How many friends she had?
Solution:
We have to divide 72 by 6 to know the answer.
Step 1: Divide the tens' digit by 6, 7/6 = 1 with remainder 1
Step 2: Multiply remainder 1 by 10, 1 x 10 = 10 and add it to ones' place, 10 + 2 = 12
Step 3: Divide 12 by 6, 12/6 = 2
Step 4: Combine the ones' and twos' place values
Answer is 12.
Solving Mental Math Problems - Practice Problems
Solving practice problems
Problem 1: Shan saved $73 and Sham saved $78. How much did they save altogether?
Problem 2: A shirt cost is $73, Pant cost is $99. Find the cost of difference of two items.
Problem 3: A wall clock costs 3 times as much as a watch. If the watch costs $51, what is the cost of wall clock?
Problem 4: Pond had 75 candies. He put the candies equally into 5 bags. How many candies were there in each bag?
Answer: 1) $151 2) $26 3) $153 4) 15
