Question

Question 70 (i)

Work out the following multiplication.
$12345679\ast 9\_\_\_\_\_\_\_\_\_\_\_\_\_\_$

Use the result to answer the following question.

What will be 12345679 $\times$ 45?

Answer 1

We have, $12345679\ast 9\_\_\_\_\_\_\_111111111$
Here, we observe that in the product all the digits are same i.e. 1, which is actually the unit digit of the product $9\times 9$. Also, total of digits in the multiplier is 9.

We have to compute, $12345679\ast 9\_\_\_\_\_\_\_\_\_\_\_\_\_\_$
Here, multiplier is 45 whose sum of digits is 9.
Thus, by conjecture we conclude that the product consists of digits 5 only as unit's digit of $9\times 5$ is 5
$\therefore$ $12345679\ast 45\_\_\_\_\_\_\_555555555\_\_\_\_\_\_\_$