I need to buy pencils for 315 students and the pencils are sold in boxes of 10. How can i use rounding to decide how many pencils to buy?

Find the next multiple of of 10 that is 320 and then divide that by 10 to get 32.

If every student receives 1 pencil, then:

315 : 10 = 31.5

Since you can't physically give a student half a pencil, you have to round up no matter what. So 31.5 rounded up to the next whole number will be 32.

Solution: 32 boxes of pencils