Mrs. Kennedy is buying pencils for each of 315 students at Hamilton Elementary. The pencils are sold in boxes of tens. How can she use rounding to decide how many pencils to buy?

Mrs Kennedy is buying pencils for 315 students.

The pencils are sold in boxes of 10.

Therefore the number of pencils she needs to buy should be a multiple of 10, so that she can buy boxes of 10 pencils each.

number of students are 315 but 315 is not a multiple of 10

so we have to round off 315 to the nearest ten, that's 320.

so then she has to buy 320 pencils

number of boxes she needs - 320 / 10 = 32 boxes of pencils

she only needs pencils for 315 students so she will have 5 extra pencils

she will have to buy 32 boxes

Since 5 is closer to 10 then it is to zero, the tens column will be pushed up by one. the answer is-

320. she will have 5 extra pencils