Question

Sandra used partial products to find the product of 438 × 17 by multiplying 438 by 1 and 438 by 7 to get 3,066. Find the product of 438 × 17 by using partial products. Is sandra correct? Compare your answer to sandra's and explain why it is or is not the same.

Answer 1

Let us determine the product of 438 and 17 by partial products.

Consider
`438 = 400+30+8`

and
`17 = 10+7`

So,
`438 * 17 = (400+30+8) * (10+7)`

`438 * 17 = (400* 10)+(30 * 10)+(8 * 10) +(400 * 7)+(30 * 7)+(8 * 7)`

=
`438 * 17 = (4000+300+80+2800+210+56)`

= 7446

Therefore, the product of 438 and 17 is 7446.

No, Sandra's answer is not correct.

Because she should have expressed 17 as (10+7), then if she multiplied (438 by 10) and (438 by 7). And, then added the results.Then her answer would be correct.