Write and solve a problem where you need to regroup to make a ten or a hundred. Explain why you needed to regroup.
Problem: Mrs. Smith bought 67 packs of pencils, each containing 10 pencils. How many pencils did she buy in total?
Solution:
To solve this problem, we need to multiply the number of packs by the number of pencils in each pack. However, since we are dealing with a number greater than 10, we need to regroup to make a ten.
67 packs x 10 pencils = 670 pencils
Therefore, Mrs. Smith bought a total of 670 pencils. We had to regroup to make a ten because multiplying 67 by 10 directly would have resulted in an incorrect answer. By regrouping, we were able to correctly calculate the total number of pencils she bought.