Saving Hundreds

Using Materials

Problem: Julia has to save $400 for a bike. She has $287 saved. How much more does Julia have to save?

Write 287 + ? = 400 on the board. Select three students and say which student will be in charge of the hundreds, tens and ones. Let the "hundreds" student count out 2 hundreds, the "tens" student count out 8 tens and the "ones" student count out 7 ones.The "ones" student is given 3 ones which he swaps for 1 ten which he gives to the "tens" student and sits down. 3 is recorded on the board. Now the tens student has 9tens and needs to get 1 ten to make 100. When she has 10 tens she swaps it for 1hundred, gives this to the "hundreds" student and sits down. Write 10 on the board. The "hundreds" student receives a hundred. Write 100 on the board. Discuss why the answer to 287 + ? = 400 is 113. Notice that the order in which the extra money isgiven out can be varied. For example the .tens. student may be given $20 initially.

Students will need to understand why, eventually, this student will have to give one of these ten dollar notes to the bank. Examples. 484 + ? = 500,  345 + ? = 400, 290 + ? = 400, 488 + ? = 600, 67 + ? = 200, …

Using Imaging

Shielding and Imaging Only:
98 + ? = 500,  345 + ? = 400, 290 + ? = 400, ? + 488 = 700, ? + 381 = 500, …

Using Number Properties

Examples. Word problems and recording for: 106 + ? = 800,  279 + ? = 700, 378 + ? = 1000, 136 + ? = 800, 809 + ? = 900, ? + 378 = 1000

Challenging examples. 2990 + ? = 5000,  546 + ? = 4000, 6 + ? = 8000, ? + 450 = 5000, ?  + 1950 = 9000, …