Question

255^2-245^2=_
Don't solve using a calculator, is there a trick to solving this without a calculator?
thanks, please don't spam!

Answer 1

Recall that

(a + b)² = a² + 2ab + b²

Then we write

255² - 245² = (245 + 10)² - 245²

… = (245² + 4900 + 10²) - 245²

… = 4900 + 100

… = 5000

Answer 2

Since they are whole numbers you can just subtract
255 - 245 = 10
The ^2 means add two decimal points after the 10 in the positive direction since it’s ^+2

So 1000

255^2 =25500
245^2 = 24500

25500 - 24500 = 1000