Concept 7 of 7
Fraction of a Group: 3/4 of 24 Marbles
Today's big idea
Divide the group by the bottom to get one part, then multiply by the top.
Sharing a bag of marbles works exactly like sharing one pizza.
How it works
👀 What's going on?
A fraction does not need a pizza. Ask for three quarters of a bag of marbles and there is nothing to cut at all, just a pile to split up. The recipe turns out to be the sharing you already know, done twice.
💡 Here's the trick
Look at the marbles above. To take 3/4 of 24, the bottom number splits the 24 into 4 equal groups of 6. The top number then takes 3 of those groups, which is 18. Divide by the bottom to find one part, then multiply by the top to take that many parts.
🪄 How to do it
- 1.Divide the group size by the bottom number, the way the marbles above are dealt into 4 equal bunches.
- 2.Multiply that one bunch by the top number.
✍️ Try it
Work out 2/5 of 20 flowers. Then work out 3/8 of 40 stickers.
For the flowers, 20 ÷ 5 = 4 in each part, and 2 parts is 2 × 4 = 8 flowers. For the stickers, 40 ÷ 8 = 5 in each part, and 3 parts is 3 × 5 = 15 stickers.
⚠️ Watch out
You might be thinking it does not matter which number you divide by. It matters completely. For 2/5 of 20, dividing by the top gives 20 ÷ 2 = 10, which is half the flowers, not two-fifths of them. The bottom number always does the dividing.
🌟 Why this matters
Half the class on a trip, a quarter of your pocket money saved, two-thirds of the balloons popped. Real fractions are usually fractions of a group.
Exam tip: If your answer comes out bigger than the group you started with, you have divided by the wrong number.
Watch me solve one
Quanta solves it
“Watch how I think through one of these — then you try.”
THE PROBLEM
“2/3 of 15 stickers = ?”
- 1
Divide by the bottom
Split 15 into 3 equal parts: 15 ÷ 3 = 5 per part.
- 2
Multiply by the top
Take 2 of those parts: 2 × 5 = 10
- 3
Answer ✓
= 10 stickers
Now you try one — same steps, different story 👇
See it in action
⚡ Time to play!
Find 3/4 of 24 marbles. Split into 4 equal groups, then take 3.
FRACTION OF A GROUP · ROUND 1 OF 3
3/4 of 24
one pile of 24
Quick check
✅ VERIFICATION
2/3 of 18 pencils = ?
⚡ Finish the activity above first to answer.
Keep going!