Any number ending in 5 can be be squared without using a calculator. Method- eg. 85^2 two step calculation 1. 5 x 5 = 25 2. take the number before the 5, in this case 8, multiple the number 8 by the next whole number which is 9, take the product 8 x 9 = 72 answer 85^2 7225 note the answer will always end in 25, simply prefix with the product.