Squaring A number In The Range (40-49)

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]  43^{2=________________}

a) The difference from 50 is 7.

b) 7² = 49. Write 49

c) 25 – 7 = 18. Write 18.

d) The answer is 1849.

Ex [2]  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 [3]  42² =_________.

a) The difference from 50 is 8.

b) 8² = 64. Write 64.

c) 25 – 8 = 17. Write 17.

d) The answer is 1764.