Today’s problem — free all day, every step. Every day has one.
Bakery countertop — coasters around the display case
The figure shows a rectangular display case and an L-shaped countertop border around it in a bakery. The width of the border is 40 cm. The border is covered with 30 circular coasters of diameter 20 cm, following the pattern shown in the figure. Each coaster touches the ones next to it. What is the area of the border not covered by the coasters? (Take π = 3.14)
Show the answerHide the answer
See all 6 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: Number × value
One batch repeats. Work out one batch, then multiply.
In this one. Pair every coaster with its own 20 cm by 20 cm square slot, find the same uncovered corner area once, then multiply that value by 30.
How to spot it
Items are described as a fixed group or ratio that repeats, such as tiles following a pattern, snacks sold in a fixed mix, or a rate given per hour or per item.
Common mistake
Children start from the grand total instead of first working out what one batch is worth. In rate questions they also confuse a duration with a clock time.
Try one like it
Standard Buns and muffins — 3 : 5 worth $55 A bakery sells buns and muffins in the ratio of 3 buns to 5 muffins. Each bun costs $2, and each muffin costs $1. If the total val…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.