ian multiplied a number by 5. he then multiplied that product by 2. what digit is in the ones place of the final product?

so he multiplied something by 5 and then by 2.

Mmmmhhh, didn't he in effect multiply by 10 ??

What happens when you multiply something by 10 ?

10

To solve this problem, we need to follow the given steps to find the final product. Let's break it down:

1. Ian multiplied a number by 5. Let's assume the number is 'x'. So, the result of this step is 5 * x.

2. Ian then multiplied that product by 2. The previous step's result was 5 * x. Now we multiply it by 2 to get the final result, which is (5 * x) * 2.

To find the digit in the ones place of the final product, we need to focus on the units place of each multiplication involved. Since 5 multiplied by any digit will always end in either 0 or 5, multiplying it by 'x' won't change the units place.

The units place of any even number multiplied by 2 will always be 0, and for any odd number multiplied by 2, it will be 2.

Considering this information, we know that the final product (5 * x) * 2 will have the digit 0 in the ones place since both 5 * x and 2 are even numbers.

Therefore, the digit in the ones place of the final product is 0.