Problems like 23 + ……. . = 71 I am learning to solve problems like 13 + ……. = 91 by jumping up by a tidy number on a number line, then jumping back a small number Numbers like 10, 20, 30, 40 etc. Means add (+) Means subtract ( -)
SAMPLE PROBLEM Sam lives at the green house which is number 34 on the number line. How many numbers does he have to pass to get to number 82 where his friend lives? 34 + ? = 82
SAMPLE PROBLEM 34 + ? = 82 Step 1: Draw a number line with your starting point and end point.
SAMPLE PROBLEM 34 + ? = 82 Step 2: Choose a tidy number to jump up which takes you just past your target. Then write it on your number line. 60 Takes me way to far. I will Adding 40 only gets me to have to try again 74. That’s not far enough! 50 takes me just past 82 so this is the best number to jump.
SAMPLE PROBLEM 34 + ? = 82 Step 3: Jumping up 50 took me a little too far. I now have to jump back 2 so I can get to number 82
SAMPLE PROBLEM 34 + ? = 82 Step 4: You jumped up 50 and back 2 (50 – 2). So you jumped up 48 numbers. Than means… 34 + 48 = 82
Now let’s try one together Fred the frog lives on lily pad 15. He wants to visit his friend on lily pad number 61. How far does he need to jump? 15 + ? = 61
Now let’s try one together 15 + ? = 61 Step 1: Draw a number line with your starting point and end point. Do this now on a piece of paper.
Now let’s try one together 15 + ? = 61 Step 2: Choose a tidy number to jump up which takes you just past your target number (61). Do this now.
Now let’s try one together 15 + ? = 61 Step 3: Now find the number you must jump back to get to your target number. Add this to your drawing now.
Now let’s try one together 15 + ? = 61 Step 4: Now work out how far you had to jump. (subtract your little jumps back from your big jump up. ) Do this now. So… 15 + 46 = 61
Now try these questions on your own. 1) 17 + ? = 24 6) 18 + ? = 59 2) 23 + ? = 62 7) 12 + ? = 71 3) 56 + ? = 82 8) 56 + ? = 82 4) 34 + ? = 63 9) 34 + ? = 41 5) 15 + ? = 91 10) 15 + ? = 42
Only click again if you have completed all the questions on the previous slide and you are ready to see the answers. 1) 7 6) 41 2) 39 7) 59 3) 26 8) 26 4) 29 9) 7 5) 76 10) 27 Need some more practise? Try Pg 46 of Teacher Tools Addition and Subtraction Book Numeracy resources
