do you round up/ down the answer as you cant own an eighth of a shoe. or do you answer exact including the decimal point??

Question

Percentage problem solving, do you round up/ down the answer if the subject are shoes, Apple's, cars etc? Eg Mrs Smith owns 73 pairs of shoes and 50 percent are high heels. How many shoes are high heeled? Its for a year 6 student. Thanks

Answer 1

Hi Norma,
 
Neither !!
 
First, PLZ distinguish between rounding a calculation up/down and rounding to a whole object.
 
For example, this problem states that " 51% of shoes..." -- that is the answer, not the starting value.  First, the total number of shoes and the number of high-heals were counted, then the ratio was created and a percent was calculated,  THEN the resulting answer was rounded (note: the shoes were not rounded).  So, working backwards, the problem is really saying that the true percentage of high-healed shoes is such that rounding that value produces 51%.
 
Working forward, there are 73 shoes, if 36 of them are high-heals, that is 49% (49.3 rounded down).  If 37 of then are high-healed, that is 51% (50,68 rounded up).  If 38 are high-heals, that is 52%.  So, conclusively, the answer is 37 (note: I did not round shoes either up or down! and rounding shoes might have produced the wrong answer!!!).
 
Thinking this way is well within the capability of year 6 student if it is explained in a verbose way with lots of examples.
 
Best wishes.
(p.s., I've worked with graduate-level people who "never thought of that."

Answer 2

Hi Norma,

Yes, you should round down in this scenario. When the item is not divisible (ie. cannot be cut into parts), then you should round. If the item is divisible (ie. can be cut into smaller pieces), then you can give the exact value.

Example:

Indivisible - shoes, cars

Divisible - cups of milk, square feet of carpet