Order of operations and brackets · Usually met around P3
Bar models for word problems
Draw the bars, then see where the “?” is.
How to do it
Method
Draw the bars, then see where the “?” is
Whole 45, one part 18: 45 − 18 = 27
Another way
Check with a number sentence
18 + 27 = 45
In full
A bar model draws a word problem. Part and whole: one bar stands for the whole, cut into the parts; part + part = whole, so add to find the whole, and take the other parts from the whole to find a part. Comparing two amounts: draw one bar above the other, lined up on the left; the bigger amount has the longer bar, and the extra stretch is the difference. Add to find the bigger amount; take away to find the smaller or the difference. Where the “?” goes shows what to find. Or write the number sentence first and check it with the bars: smaller + difference = bigger.
Worked examples
Have a go first, then open each one for the answer and the working.
Example 1
Look at the bar model. What number does “?” stand for?
Show the answer and working
Answer: 117
“?” is the whole: part + part = whole, 72 + 45 = 117.
Example 2
Look at the bar model. What is the difference between A and B?
Show the answer and working
Answer: 68
The extra stretch is the difference: bigger − smaller, 90 − 22 = 68.
Example 3
Look at the bar model. Which number sentence finds how much A has?
- A. 51 + 10
- B. 51 + 51 − 10
- C. 51 − 10
- D. 10
Choose the right answer
Show the answer and working
Answer: C. 51 − 10
Smaller = bigger − difference: 51 − 10 = 41.
Practise it in the game →Order of operations and brackets · Free to start, unlimited questions, no download