Question

Find, where we get big number among the following pairs without multiplying them? 

(i) 25 × 75, 26 × 74 

(ii) 76 × 24 . 74 × 26 

(iii) 10.6 × 9.6 

(iv) 10.4 × 9.6

Answer 1

(i) 26 × 74

(ii) 74 × 26

(iii) 10.6 × 9.6

Indications

25 × 75 = (50 – 25) (50 + 25)

= 50² – 25²

26 × 74 = (50 – 24) (50 + 24)

= 50² – 24²