Question

Mental math

(i) (83 × 12) + (17 × 12)

(ii)

(iii) (3.7 × 19) + (6.3 × 19)

(iv) (137 × 13) − (37 × 13)

(v)

Answer 1

(i) (83 × 12) + (17 × 12)

= (83 + 17) × 12 {Using xz + yz = (x + y) z}

= 100 × 12

= 1200

(ii)

(iii) (3.7 × 19) + (6.3 × 19)

= (3.7 + 6.3) × 19 {Using xz + yz = (x + y) z}

= 10 × 19

= 190

(iv) (137 × 13) − (37 × 13)

= (137 − 37) × 13 {Using xz − yz = (x − y) z}

= 100 × 13

= 1300

(iv)