Post on 14-Jan-2016
You have already found percents using the percent proportion. (Lesson 7–3)
• Compute mentally with percents.
• Estimate with percents.
Use a Fraction to Compute Mentally
A. Find 50% of 46 mentally.
Answer: 50% of 46 is 23.
THINK:
THINK:
Use a Fraction to Compute Mentally
= 6
A. 41
B. 164
C. 16
D. 40
A. Find 50% of 82 mentally.
A. 6
B. 4
C. 16
D. 48
B. Find 25% of 24 mentally.
Use Decimals to Compute Mentally
A. Compute 10% of 54 mentally.
Answer: 5.4
10% of 54 = 0.1 ● 54 or 5.4
Use Decimals to Compute Mentally
B. Compute 1% of 219 mentally.
Answer: 2.19
1% of 219 = 0.01 ● 219 or 2.19
Use Decimals to Compute Mentally
C. Compute 20% of 50 mentally.
Answer: 10
First, find 10% of 50 = 0.1 ● 50 or 5
Then, 20% is 2 ● 10%, so 20% of 50 = 2(10% of 50)
= 2(5)
= 10
Use Decimals to Compute Mentally
D. Compute 15% of 40 mentally.
Answer: 6
First, find 10% of 40 = 0.1 ● 40 or 4
= 2
Think of 15% as 10% + 5%
Finally add (10% of 40) + (5% of 40) = 4 + 2
= 6
A. 0.089
B. 0.89
C. 8.9
D. 890
A. Find 10% of 89 mentally.
A. 0.0543
B. 0.543
C. 5.43
D. 54.3
B. Find 1% of 543 mentally.
A. 56
B. 8
C. 24
D. 16
C. Find 30% of 80 mentally.
A. 6
B. 3
C. 9
D. 30
C. Find 15% of 60 mentally.
Compute Mentally
SHOPPING Garrett is shopping for a new video game. The original price of the game is $60.00. The game is 10% off. How much will Garrett save?
Find 10% of $60.
10% of 60 = 0.10 ● 60 Move the decimal pointone place to the left.
= 6
Answer: Garrett will save $6.
A. $4.20
B. $21.00
C. $42.00
D. $84.00
John has a coupon for a 10% discount. If he buys a television with a regular price of $420, how much will he save?
Estimate Percent of a Number
A. Estimate 22% of 494.
Answer: So, 22% of 494 is about 100.
Estimate Percent of a Number
B.
So,
Estimate Percent of a Number
C. Estimate 49% of 61.
Answer: So, 49% of 61 is about 30.
61 is about 60.
Estimate Percent of a Number
D. Estimate 155% of 38.
Answer: So, 155% of 38 is about 40 + 20 or 60.
155% is about 150%. 38 is about 40.
100% of 40 is 40. 50% of 40 is 20.
A. 100
B. 152
C. 160
D. 80
A. Estimate 38% of 400.
A. 25
B. 4.964
C. 4
D. 5
B. Estimate % of 2482.
C. Which is the best estimate for 26% of 78?
A. 10
B. 20
C. 25
D. 30
A. 135
B. 46.5
C. 49.29
D. 180
D. Estimate 153% of 93.