Page 871 - Algebra 1

Mental Math
Skills Bank Lesson 11
Mental math means to find an exact answer quickly in your head. Mental math strategies use number properties.
Using Properties to Add or Multiply Whole Numbers
a. Find the sum of 32 + 3 + 48 + 57. SOLUTION
Example
1
32 + 3 + 48 + 57
= 3 + 57 + 32 + 48
= (3 + 57) + (32 + 48) = 60 + 80
= 140
b. Find the product of SOLUTION
2 · 44 · 5
= 2 · 5 · 44 = (2 · 5) · 44 = 10 · 44
= 440
Look for sums that are multiples of 10. Use the Commutative Property.
Use the Associative Property.
Add.
2 · 44 · 5.
Look for products that are multiples of 10. Use the Commutative Property.
Use the Associative Property.
Multiply.
c. Find the product of 8 · 47. SOLUTION
8 · 47
8 · 47 = 8 · (40 + 7)
= (8 · 40) + (8 · 7) = 320 + 56
= 376
Skills Bank Practice
Find each sum or product. a. 24+15+16+15 c. 58·4
e. 34·7
g. 8+67+12+3
“Break apart” 47 into 40 + 7. Use the Distributive Property. Multiply.
Add.
b. 6·12·5
d. 6+31+34+9
f. 4·62·25 h. 33·9
856 Saxon Algebra 1