← Back to course
Ratios and Data 6-8 / Week 03 / Wednesday
3/6
Week 03 · Percents

Wednesday

Numbers Lab: Counter percents
// A rate per 100
⏱ about 20 min

Wednesday: Numbers Lab: Counter Percents

Rocket pours a bag of dried beans onto the Numbers Desk tray. "A hundred of them. I counted."

Raven slides a sheet of graph paper under the pile. "Then lay them out in ten rows of ten."

Nova hovers above the grid as the rows fill in. "Now flip 20 of them over, or swap in 20 paper squares."

"Twenty out of a hundred," Rocket says. "Twenty percent. That is easy with 100."

"What do you notice if we only had 20 beans?" Raven asks, sweeping most of them back into the bag.

Rocket flips 5 of the 20. "Five out of 20. Not per 100." He pauses. "But 5 out of 20 is 25 out of 100."

"Twenty-five percent," he says. "Even without a hundred."

Your mission

Build sets of counters, make some of them a different color, and write the percent each set shows.

Start with 100 so the percent is just the count. Then use smaller sets and scale each fraction to 100.

  • About 100 small counters: dried beans, buttons or paper squares
  • About 25 counters of a second color, or paper squares to swap in
  • Graph paper or plain paper, a marker and your Numbers Notebook
Safety first
Small counters stay away from children under three and from pets. Pick up every one at the end.
Nothing in the lab goes in anyone's mouth, even dried beans. Wash hands after.
Work over a tray so a spill stays on the table, not the floor.
  1. Lay out 100 counters in ten rows of ten. Swap 20 for the second color. Write the percent.
  2. Make Set 1: 20 counters with 5 of the second color. Write the fraction, then scale it to 100.
  3. Make Set 2: 10 counters with 3 of the second color. Make Set 3: 25 counters with 5.
  4. Make Set 4: 50 counters with 20. For each set, write the fraction, the decimal and the percent.
  5. Record every set in your data table.
SetCountersSecond colorFractionPercent
Set 12055/2025%
Set 21033/1030%
Set 32555/2520%
Set 4502020/5040%
THE CREW'S SETS
  • Read the question.
  • Tap your answer.
Set 1 has 20 counters and 5 are the second color. What percent is the second color?
Set 2 has 10 counters and 3 are the second color. What percent is that?
Set 4 has 50 counters and 20 are the second color. What percent is that?
SCALE IT TO 100
  • Read the question.
  • Tap your answer.
In Set 1, 5 of 20 counters are the second color. Out of 100 counters, how many would be?
In Set 3, 5 of 25 counters are the second color. Out of 100 counters, how many would be?
Set 4 is 40% the second color. It has 50 counters. How many are the second color?
Number sentenceTrue or false?
5/20 = 25/100?
3/10 = 3/100?
5/25 = 20/100?
20/50 = 40/100?
WHY THIS EXERCISEEvery percent is a fraction scaled to 100, which is exactly what the counters show.
Set 3 has 25 counters and 5 are the second color. What percent is the second color? Type the number.
WHY THIS EXERCISEScaling a small set to 100 is the move that makes any count a percent.
Try it
Build a set of your own size, like 40 counters, and pick how many to make the second color.
Predict the percent before you scale the fraction. Then check.
Draw Set 1 as two rows of 10 counters, with 5 shaded. Write its fraction, decimal and percent.

Careful counting. Tomorrow the whole sign-up sheet gets turned into percents.

← Tuesday