Definition of Mental Math
Definition: Mental math practice comprises arithmetical calculations using only the human brain, with no help from calculators, computers, pen and paper. People use mental math when those tools are not available, when it is faster than other means of calculation or in a competition context. Mental math calculation often involves the use of specific techniques devised for specific types of problems. In this lesson we will discuss about definition of mental math with example problems.
Source wikipedia.
Definition of Mental Math – Example Problems
These example problems will shows you to how to do the mental math.
Example 1: Sofia has $94 and Jack has $49. How much dollar did they has altogether?
Solution:
We have to add 94 and 48 to know the sum.
Step 1: Add the two ones' place digits of 94 and 49: 4 + 9 = 13.
Step 2: Add the two tens' place digits of 94 and 49: 9 + 4 = 13.
Step 3: Sum of the ones' place digits is two-digit number, so decrease the ones' place sum by 10: 13 - 10 = 3 and increase the tens' place sum by 1: 13 + 1 = 14.
Step 4: Combine the tens' and ones' place sums.
Answer is $143.
Example 2: A cricket ball cost is $18. A bat cost is $65. Find the difference between the cost of ball and bat.
Solution:
We have to subtract 18 from 65 to know the difference.
Step 1: Subtract the two tens' place digits of 18 and 65: 6 - 1 = 5
Step 2: Bottom ones' digit is larger than the top ones' digit.
So, decrease the answer of the tens' place by 1: 5 - 1 = 4, and increase the top ones' place value by 10: 5 + 10 = 15.
Step 3: Subtract the two ones' place values: 15 - 8 = 7
Step 4: Combine the tens' and ones' place value.
Answer is $47.
Example 3: A ball cost is $8, what is the cost of 45 balls?
Solution:
We have to multiply 45 by 8 to know the answer.
Step 1: Multiply the ones' digit of 45 by 8: 45 x 8 = 40
Step 2: Multiply the tens' digit of 45 by 8: 45 x 8 = 32
Step 3: Product of ones' place is two digits (40), so increase the product of tens' digit by 4: 32 + 4 = 36
Step 4: Combine the ones' and twos' place value
Answer is $360.
Example 4: Jessica had 72 chocolates. She gave 4 chocolates to each her friend. How many friends she had?
Solution:
We have to divide 72 by 4 to know the answer.
Step 1: Divide the tens' digit of 72 by 4: 72 / 4 = 1 (Remainder 3)
Step 2: Multiply the remainder 3 by 10, 3 x 10 = 30, and add it to ones' place of 72, 30 + 2 = 32
Step 3: Divide 32 by 4, 32 / 4 = 8
Step 4: Combine the ones' and twos' place values
Answer is 18.
I have recently faced lot of problem while learning Examples of Piecewise Functions, But thank to online resources of math which helped me to learn myself easily on net.
Definition of Mental Math – Practice Problems
Problem 1: Sofia has $85 and Jack has $35. How much dollar did they has altogether?
Problem 2: A cricket ball cost is $15. A bat cost is $70. Find the difference between the cost of ball and bat.
Problem 3: A ball cost is $7, what is the cost of 53 balls?
Problem 4: Jessica had 51 chocolates. She gave 3 chocolates to each her friend. How many friends she had?
Answer: 1) $120 2) $55 3) $371 4) 17
Definition: Mental math practice comprises arithmetical calculations using only the human brain, with no help from calculators, computers, pen and paper. People use mental math when those tools are not available, when it is faster than other means of calculation or in a competition context. Mental math calculation often involves the use of specific techniques devised for specific types of problems. In this lesson we will discuss about definition of mental math with example problems.
Source wikipedia.
Definition of Mental Math – Example Problems
These example problems will shows you to how to do the mental math.
Example 1: Sofia has $94 and Jack has $49. How much dollar did they has altogether?
Solution:
We have to add 94 and 48 to know the sum.
Step 1: Add the two ones' place digits of 94 and 49: 4 + 9 = 13.
Step 2: Add the two tens' place digits of 94 and 49: 9 + 4 = 13.
Step 3: Sum of the ones' place digits is two-digit number, so decrease the ones' place sum by 10: 13 - 10 = 3 and increase the tens' place sum by 1: 13 + 1 = 14.
Step 4: Combine the tens' and ones' place sums.
Answer is $143.
Example 2: A cricket ball cost is $18. A bat cost is $65. Find the difference between the cost of ball and bat.
Solution:
We have to subtract 18 from 65 to know the difference.
Step 1: Subtract the two tens' place digits of 18 and 65: 6 - 1 = 5
Step 2: Bottom ones' digit is larger than the top ones' digit.
So, decrease the answer of the tens' place by 1: 5 - 1 = 4, and increase the top ones' place value by 10: 5 + 10 = 15.
Step 3: Subtract the two ones' place values: 15 - 8 = 7
Step 4: Combine the tens' and ones' place value.
Answer is $47.
Example 3: A ball cost is $8, what is the cost of 45 balls?
Solution:
We have to multiply 45 by 8 to know the answer.
Step 1: Multiply the ones' digit of 45 by 8: 45 x 8 = 40
Step 2: Multiply the tens' digit of 45 by 8: 45 x 8 = 32
Step 3: Product of ones' place is two digits (40), so increase the product of tens' digit by 4: 32 + 4 = 36
Step 4: Combine the ones' and twos' place value
Answer is $360.
Example 4: Jessica had 72 chocolates. She gave 4 chocolates to each her friend. How many friends she had?
Solution:
We have to divide 72 by 4 to know the answer.
Step 1: Divide the tens' digit of 72 by 4: 72 / 4 = 1 (Remainder 3)
Step 2: Multiply the remainder 3 by 10, 3 x 10 = 30, and add it to ones' place of 72, 30 + 2 = 32
Step 3: Divide 32 by 4, 32 / 4 = 8
Step 4: Combine the ones' and twos' place values
Answer is 18.
I have recently faced lot of problem while learning Examples of Piecewise Functions, But thank to online resources of math which helped me to learn myself easily on net.
Definition of Mental Math – Practice Problems
Problem 1: Sofia has $85 and Jack has $35. How much dollar did they has altogether?
Problem 2: A cricket ball cost is $15. A bat cost is $70. Find the difference between the cost of ball and bat.
Problem 3: A ball cost is $7, what is the cost of 53 balls?
Problem 4: Jessica had 51 chocolates. She gave 3 chocolates to each her friend. How many friends she had?
Answer: 1) $120 2) $55 3) $371 4) 17
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