← Back to course
Ratios and Data 6-8 / Week 03 / Data Day
6/6
Week 03 · Percents

Data Day

Data Day: Percent hunt
// A rate per 100
⏱ about 20 min

Data Day: Percent Hunt

Saturday morning the family gathers at the Numbers Desk with every charger in the house.

"Percent hunt," Raven announces. "Find a percent, name its whole, and find its part."

Rocket checks the tablet. "Sixty percent. The whole is a full battery." He pauses. "But how big is that?"

"What do you notice about the number on the back of the charger?" Raven asks. "It says 20 watt-hours," Rocket reads.

Nova hovers over the charger. "Then 60% of 20 is your part."

"Twelve," Rocket says. "Twelve watt-hours left. I never knew a battery was a math problem."

  1. A percent is a rate per 100. The sign % means out of 100, and a hundred grid is its picture.
  2. To find a percent of a number, multiply by the fraction over 100, or find 10% first.
  3. To find the whole from a part and a percent, find 1% or 10% first, then 100%.
  4. Percents, fractions and decimals name the same number: 25% = 1/4 = 0.25.
  5. Every real percent has a whole behind it. Ask what the whole is before you use the number.
◇ FAMILY PERCENT HUNT
Find five percents around the house: battery levels, a progress bar, a label, a game score.
For each one, say the whole and work out the part. A battery at 60% of 20 units has 12 units left.
Pick one and write it three ways: as a percent, a fraction and a decimal.
Take turns making up a find-the-whole puzzle, like "9 is 45% of my number." Solve each other's puzzles.
For a grown-up
This week your student learned that a percent is a rate per 100. They found percents of numbers and a whole from a part.
Ask them to explain the 10% trick: find 10% by dividing by 10, then build the percent you need.
Chargers and devices stay plugged in or unplugged by you. Reading the label is the whole job.
PERCENT HUNT CHECK
  • Read the question.
  • Tap your answer.
A battery is at 60% and holds 20 units when full. How many units are left?
A game shows 14 of 20 levels done. What percent is done?
Rocket says 9 is 45% of his number. What is his number?
Which percent equals 3/5?
StatementTrue or false?
60/100 × 20 = 12?
14/20 = 70/100?
A percent is a rate per 100.?
A percent makes sense without knowing the whole.?
WHY THIS EXERCISEThe whole is the question to ask every time you meet a percent.
Draw a hundred grid shaded to match your favorite percent from the hunt. Label the whole.
← Friday