Balance puzzles and ratio
Loading…
What you will learn
By the end, you can solve ? + 4 = 11 and 3x + 2 = 14, and share 20 sweets in the ratio 2:3.
At the market, a trader puts a mystery bag and 3 apples on one side of a balance scale, and 10 apples on the other. The scale sits level. Take 3 apples off each side and it still sits level, so the bag must weigh the same as 7 apples.
Read the explanation
A balanced scale stays level when both sides hold the same amount. Take the same amount off both sides and it stays level: that is how you uncover a missing number. Ratio is fair sharing with a rule: 2:3 means 2 parts for one person and 3 for the other, so the total is split into 5 equal parts.
- Undo what was done: take away what was added, then divide by what was multiplied.
- Ratio a:b makes a + b parts. One part = total ÷ number of parts.
- Check by putting your answer back in: 3 × 4 + 2 = 14.