50% of a number is 90. Find the number and check.
180
Whole = 90 ÷ 1/2 = 180. Check 50% × 180 = 90.
Day 059Choosing a Percent Strategy
Standards 6.RP.A.3c
LEARNING TARGET
I can identify the unknown in a percent problem and select a strategy.
01 · LEARN
Build the idea
Read the requested quantity first and identify the relevant model. Use part = (percent/100) × whole. You may also find 10%, 5%, or 1% and combine equal pieces. Label the part in the same units as the whole. Explain why the units and the final value fit the situation.
30 students are 75% of a school’s enrollment. Find the enrollment.
40
Whole = 30 ÷ 3/4 = 40. Check 75% × 40 = 30.
02 · PRACTICE
Your turn
Work in order. Start with the foundations, then build toward explanation and application.
Find 20% of 180.
10% of a number is 12. Find the number and check.
16 is what percent of 160?
Find 75% of 200.
125% of a number is 200. Find the number and check.
48/5 is what percent of 80?
Find 30% of 180. Then explain a mental-math or fraction strategy that checks your answer.
9 students are 5% of a school’s enrollment. Find the enrollment.
200 is what percent of 160? State which quantity is the reference whole.
Find 30% of 60. Then explain a mental-math or fraction strategy that checks your answer.
03 · CHECK
Answers and reasoning
Reveal the teacher answer key
- 36
20/100 × 180 = 36.
- 120
Whole = 12 ÷ 1/10 = 120. Check 10% × 120 = 12.
- 10%
16 ÷ 160 × 100 = 10%; the reference whole is 160.
- 150
75/100 × 200 = 150.
- 160
Whole = 200 ÷ 5/4 = 160. Check 125% × 160 = 200.
- 12%
48/5 ÷ 80 × 100 = 12%; the reference whole is 80.
- 54
30/100 × 180 = 54.
- 180
Whole = 9 ÷ 1/20 = 180. Check 5% × 180 = 9.
- 125%
200 ÷ 160 × 100 = 125%; the reference whole is 160.
- 18
30/100 × 60 = 18.