Today’s problem — free all day, every step. Every day has one.
Flour — Mrs Tan's cake and cookies
Mrs Tan used of her flour to bake a cake and of the remainder for cookies. What fraction of the flour was left?
See all 7 steps
MathBrush is being tested with a few parent groups, and every solution on the site is open to them — one household, all children. If you were given a code, it goes in once and this device remembers it.
I have a code → See a free one like it
65 worked examples are free without a code, two from every pattern. No account, either way.
The pattern behind it: Branching
The second fraction is of one piece, not of the whole.
In this one. The second fraction bites into the remainder, not the whole — so 1/4 of the remainder is 1/4 of 1/3 = 1/12, and what survives is 3/4 of that third. (The trap: 1/3 − 1/4 = 1/12. That subtracts a quarter of the whole, which is not what happened.)
How to spot it
A second fraction arrives after the first and is attached to a piece rather than to the whole — 'of the remainder', 'of what was left', or 'of the ones that were red'.
Common mistake
Children take the second fraction of the original total instead of the piece it was named against, which makes the amount come out too big.
Try one like it
Standard A dress and a handbag — Mei's savings Mei spent $48 on a dress. This was 3/8 of her savings. After buying the dress, she spent 1/5 of the remaining savings on a handbag…The 33 problem patterns
All 33 patterns, one to a page — the 19 behind Primary 5 and 6 word problems, and the skills the younger years are built on. The bar model, how to spot it in the question, and the mistake children make. A booklet you can print. Free.
A PDF, and a note when new solutions go up.