Multiplying money amounts - 4th grade math: estimation and word problem
In this 4th grade math lesson, we first practice multiplying money amounts and estimating the final result. Secondly, I work through a word problem that involves money, using a bar model to help.
The lesson continues with some word problems. In the first one, we can round the price $11.95 up to $12, which is just five cents more than the real price. Then, to find the price of four items, we can go 4 × $12 = $48, which is 4 × 5 cents too much... so the real total is $47.80. The question is asking for change from $50, which is now easy to figure out by adding up (mental math).
In the second problem, we find out how many $0.80 cookies you can get with $20. It turns out, instead of using division, it's easier to use multiplication and mental math to find the answer.
See also
Use mental math (partial products) to multiply
Math Mammoth Grade 4 curriculum