Question

Hailey is fixing a gap in a wooden bookshelf. To fit well, she needs a piece of wood that measures 3.2 inches long.
A. She decides that as long as the length rounds to 3.2 inches, it will work. She has several pieces of wood to choose from. Which of the pieces of wood below can she use for her project?
3.26 inches, 3.209 inches, 3.18 inches, 3.30 inches, 3.09 inches




B. She later realizes that if the wood is longer than 3.2 inches, even by a tiny amount, she can't use it. Instead, she needs to find a piece of wood that rounds to 3.2 inches, but is no longer than 3.2 inches. Which piece of wood should she use?

Answer 1

Part A) for rounding to a certain decimal place, look at that decimal place, go to the right one place, see whether the digit is 5+ (in which case you’d round up) or <5 (in which case you’d round down)

This is probably easier to see with 3.2 inches as our number. We look at the tenths place (0.2) and move one place over (0.2X)

Using this logic, numbers between 3.20 and 3.249999 etc. will round down to 3.2 and numbers from 3.15 to 3.1999 will round up to 3.2. Any numbers outside these bounds will round to something other than 3.2

For part B) simply look at the valid numbers you selected out of the list, and eliminate any that are above 3.2