11. Use the fact that 19 X 33 = 627 to solve the problems and justify

your reasoning

Step-by-step explanation:

We have,

19 × 33 = 627

Use the fact and justify.

L.H.S. = 19 × 33

= (20 - 1) (20 + 13)

Using the identity,

(x - a)(x + b) = - (a - b)x - ab

Here, x = 20, a = 1 and b = 13

= - (1 - 13)20 - 1(13)

= 400 - (- 12)20 - 13

= 400 + 240 - 13

= 640 - 13

= 627

= R.H.S., justified.

Thus,  19 X 33 = 627,  justified.