2
Ways to reach a target
Learner’s Book 1: Unit 13, p. 195
GoalChoose your own jumps on a number line to reach a target number.
New words
target · the number we want to reachroute · a path of jumps from the start to the targetnumber sentence · numbers and signs that tell what we did, like 10 + 3 = 13
Explanation
A target is the number we want to reach. We can choose our own jumps to get there. To get from 0 to 13 we could jump 10 and then 3. Each way gives a number sentence: 10 + 3 = 13. We can also go backwards to a target. To get from 17 to 9, we could jump back 7 to reach 10 and then jump back 1 more. That is 17 − 8 = 9. There are many different routes to the same target.
Worked examples
From 0 to 13 with jumps of 5, 5 and 3. 5 + 5 + 3 = 13.
From 0 to 13 with jumps of 8 and 5. 8 + 5 = 13. Different jumps, same target.
From 17 back to 9: jump back 7 to 10, then back 1 to 9. The two jumps together are 8, so 17 − 8 = 9.
Class activity
Target race: choose a target from 10 to 20. Start at 0 and find as many different routes as you can with 2 or 3 jumps. Write a number sentence for each. Who finds the most?
Practice
1
Start at 0. Which jumps reach 12: 10 and 2, or 8 and 3?
10 and 2
2
Start at 0. Make a route to 16 with two jumps.
Any such as 10 + 6 or 8 + 8
3
Start at 14. Which jump back reaches 6?
a jump back of 8
4
Start at 15. How many do you jump back to reach 10?
5