Use known facts to find complements to 100 efficiently

Maths

In this unit pupils will use known facts to find multiples of ten that compose 100  and use known facts to find complements to 100.  In the future unit pupils will find a 2-digit number and a 1 or 2-digit number that compose 100. Pupils will position 3-digit numbers on a number line and estimate the position of 3-digit numbers on unmarked number lines. They will compare and order 3 digit numbers.

In the prior unit pupils reviewed and secured previous knowledge of add 3 addends, understanding they can be added in any order, bridging through 10. In this unit pupils will use known facts to find multiples of ten that compose 100  and use known facts to find complements to 100.

Securing place value to 100 and applying to addition and subtraction

Complete the sentence: When the ones digits total 10 and the tens digits total {{ }} the two 2-digit numbers are complements to 100

55 + 55 = 100. Why is this calculation incorrect?

Which of these 2-digit numbers is a multiple of ten?

Jacob has 75 football cards and wants 100 football cards. How many more football cards does he need?

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