Video: KS1-M16S • Paper 2 • Question 5

KS1-M16S-P2-Q05-658154902830

02:18

Video Transcript

Sam’s arm is 50 centimetres long. Ben’s arm is 40 centimetres long. How much longer is Sam’s arm than Ben’s arm?

Let’s listen to that question again. Sam’s arm is 50 centimetres long. Ben’s arm is 40 centimetres long. How much longer is Sam’s arm than Ben’s arm? Sam and Ben are sticking out their arms, and they’ve had them measured. We know that Sam’s arm is 50 centimetres and Ben’s arm is shorter. His arm is 40 centimetres long. And so we know that Sam’s arm is longer than Ben’s arm. But how much longer? This is what the question asks us.

We need to find the difference in length between 50 and 40. We could sketch a bar model to help us. The number 50 is made up of five tens: 10, 20, 30, 40, 50. Five tens are 50. And so this first bar represents Sam’s arm length, 50 centimetres long. Now we can draw a similar bar to represent Ben’s arm length. How many tens are in 40 centimetres? We need four of these tens blocks to make a bar that’s 40 long: 10, 20, 30, 40.

Now we can see from the bar model how much greater 50 is than 40. We need one more block of 10 to make 50. The difference between 50 and 40 is 10. 50 is made up of five tens, and 40 is only made up of four tens. And so Sam’s arm is 10 centimetres longer than Ben’s arm.

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