Squaring A Number In The Range

(*) Squaring A Number In The Range (40 – 49):

A. This method comes from algebra:

(50 – a)² = 100(25 – a) + a²

B. Using numbers instead of variables we get the following:

1. Find the difference between the number and 50.

2. Square the result of step 1 and write it down (make sure it takes up 2 place values).

3. Subtract the result of step 1 from 25. Write this result.

Ex [1] 49² =_________.

a) The difference from 50 is 1.

b) 1² = 1. Write 01 to take up 2 place values.

c) 25 – 1 = 24. Write 24.

d) The answer is 2401.

Ex [2] 42² =_________.

a) The difference from 50 is 8.

b) 8² = 64. Write 64.

c) 25 – 8 = 17. Write 17.

d) The answer is 1764.