2. Check if     (a)    25 × (–21) = (–25) × 21         (b)    (–23) × 20 = 23 × (–20)

Write five more such examples.

Answers (1)

We know, when multiplying a positive integer and a negative integer, we multiply them as whole numbers and put a minus sign (–) before the product. We thus get a negative integer.

(a)    25 \times (-21) = (-25) \times 21         

L.H.S = 25 \times (-21) = -(25\times21) = -525

R.H.S = (-25) \times 21 = -(25\times21) = -525

Therefore, L.H.S = R.H.S

(b)   (-23) \times 20 = 23 \times (-20)

L.H.S = (-23) \times 20 = -(23\times20) = -460

R.H.S = 23 \times (-20) = -(23\times20) = -460

Therefore, L.H.S = R.H.S

Five more examples:

\\ 20 \times (-1) = (-20) \times 1 \\ 15 \times (-20) = (-15) \times 20 \\ 3 \times (-2) = (-3) \times 2 \\ (-10) \times 5= 10\times (-5) \\ (-50) \times 110= 50\times (-110)

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