Question

The estimated answer to a multiplication problem is 800,000. Which of the following expressions could result in this answer? Explain how you know.
8,146 x 12
81,467 x 121
8,146 x 121
81,477 x 1,217

Answer 1

Answer:

8,146 x 121

Step-by-step explanation:

This is a problem in which you need to measure your understading of "orders of magnitude."

If the estimated answer is $800000$ that means that we are looking at a multiplication in the "order of" $8*10^5$

You need to look at the "orders of magnitude" of the things you're multiplying. In the first case, we have $8146*12$ that would be "of the order of" $8*10^3$ times $10^1$. So the whole multiplication would "of the order of" $8*10^4$ or near $80000$

The correct answer, 8,146 x 121, is because it's "of the order of" $8*10^3$ times $10^2$ and the gives us the $8*10^5$ we need.