Use the product (a + b)(a - b) = a^2−b^2 to evaluate : (i) 21*19 (ii) 33*27 (iii) 103*97 (iv) 9.8*10.2 (v) 7.7*8.3 (vi) 4.6*5.4

Paul Gallegos

Paul Gallegos

Answered question

2023-02-28

Use the product (a + b)(a - b) = a^2−b^2 to evaluate :
(i) 21*19
(ii) 33*27
(iii) 103*97
(iv) 9.8*10.2
(v) 7.7*8.3
(vi) 4.6*5.4

Answer & Explanation

Mathew Middleton

Mathew Middleton

Beginner2023-03-01Added 3 answers

( i ) 21 × 19 = ( 20 + 1 ) ( 20 1 ) = ( 20 ) 2 ( 1 ) 2 = 400 1 = 399 ( i i ) 33 × 27 = ( 30 + 3 ) ( 30 3 ) = ( 30 ) 2 ( 3 ) 2 = 900 1 = 891 ( i i i ) 103 × 97 = ( 100 + 3 ) ( 100 3 ) = ( 100 ) 2 ( 3 ) 2 = 10000 9 = 9991 ( i v ) 9.8 × 10.2 = ( 10 .2 ) ( 10 .2 ) = ( 10 ) 2 ( .2 ) 2 = 100 .04 = 99.96 ( v ) 7.7 × 8.3 = ( 8 .3 ) ( 8 + .3 ) = ( 8 ) 2 ( .3 ) 2 = 64 .09 = 63.91 ( v i ) 4.6 × 5.4 = ( 5 .4 ) ( 5 + .4 ) = ( 5 ) 2 ( .4 ) 2 = 25 .16 = 24.84

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