Question

A scientist has 5,374 microbes growing in a dish. Fifteen minutes later there are 3,224 more microbes in the same dish. Estimate the new number of microbes in the dish by rounding each number to the nearest hundred.

Answer 1

We have 5374 microbes in a dish.

Then, 3224 more microbes are present in the dish.

We have to add them without a calculator by rounding the numbers to the nearest hundred:

$\begin{gathered} n=5374+3224 \\ n\approx5400+3200 \\ n\approx8600 \end{gathered}$

Answer: the new number of microbes in the dish is approximately 8600.