Lesson Objectives
By the end of today’s lesson you will be able to:
1)Estimate products using mental math.
2)Estimate quotients using compatible numbers.
Estimating Products
Estimate each product.
1) 7.65 × 3.2
2) 6.43 × 4.7
Estimating Products
Estimate each product.
3) 4.56×7.02
≈ 35
4) 6.3×9.2
≈ 54
5) 3.29×58
≈180
Estimating Products
Josh bought 3 yards of fabric to make a
flag. Fabric costs $5.35 per yard. The
clerk says his total is $14.95 before tax.
Did the clerk make a mistake?
Estimating Products
You buy 24 donuts from the Donut Emporium
in Plano. Each donut costs $.98 . Estimate
the cost before tax for 2 dozen donuts?
≈ $24
Objective #1
Can you…
~ estimate products using mental math?
Let’s Check…
Check for Understanding
Estimating Quotients
6÷3=2
The first number is the dividend.
The second number is the divisor.
The number after the = sign is the quotient.
Estimating Quotients
Name the following:
18 ÷3 = 6
3 is the:
18 is the:
6 is the:
Estimating Quotients
defn: compatible numbers:
-numbers easy to divide mentally
*When dividing, you can use compatible
numbers to estimate quotients
Estimating Quotients
When you estimate the quotient:
1)Round the divisor.
2)Round the dividend to a compatible
number.
Estimating Quotients
Estimate the quotient using compatible
numbers.
1)
14.9 ÷ 2.8
2) 25.3 ÷ 4.9
Estimating Quotients
Estimate the quotient using compatible numbers.
3) 35.8÷3.8
≈9
4) 29.4÷1.8
≈ 15
5) 49.6÷4.4
≈ 10
Estimating Quotients
The cost to ship 1 yearbook is $3.12. The total cost
for a shipment was $62.40. Estimate how many
books were in the shipment.
1) Round the divisor.
2) Round to a multiple of 3.
3) Find the quotient.
Estimating Quotients
Use estimation. Is each quotient reasonable?
1) 17.931÷8.34 =2.15
31.423÷5.94=3.29
2)
Estimating Quotients
Use estimation. Is each quotient reasonable?
3) 318.274÷4.07=78.2
Reasonable
4) 41.09÷6.88=5.12
Not Reasonable
Objective #2
Can you…
~ estimate quotients using compatible
numbers?
Let’s Check…
Check for Understanding
Next, compare answers with a neighbor.
18) ≈5
19) ≈6
21) ≈15
Estimating Decimal
Products and Quotients
Ask yourself if you can do the following:
1)Estimate products using mental math.
2)Estimate quotients using compatible numbers.