Question

a) Which of the following solutions do not follow the rules of multiplication? (i) 23 × (−2) = (−46) (ii) (−3) × (−13) = (−39) (iii) 18 × 5 = 90 (iv) (−9) × 6 = (−54) ​

Answer 1

Answer:

option 2

-3 x -13 =39 cause -sign and -minus sign cancel out.

Answer 2

Given :

(i) 23 × (−2) = (−46)

(ii) (−3) × (−13) = (−39)

(iii) 18 × 5 = 90

(iv) (−9) × 6 = (−54)​

To Find : Which one do not follow the rules of multiplication

Solution:

rules of multiplication with signs are :

( + ) × ( + )  = ( + )

( + ) × (- )  = ( - )

( - ) × ( + )  = ( - )

( - ) × ( - )  = ( + )

no sign means + sign.

(i) 23 × (−2) = (−46)

( + ) × (- )  = ( - )   Hence rule is followed

(ii) (−3) × (−13) = (−39)

Here ( - ) × ( - )  = (- )

while correct is  ( - ) × ( - )  = ( + )

Hence rule is not followed

(iii) 18 × 5 = 90

( + ) × ( + )  = ( + )   Hence rule is followed

(iv) (−9) × 6 = (−54)​

( - ) × ( + )  = ( - ) Hence rule is followed

Learn More:

Use BIDMAS and put the correct operator in the box. 2 6 −12 ÷ (4 + ...

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------------ sign is often dropped before a bracket and between .