How many hours are required to build 210 snowballs in the following case?Justin is making snowballs to build a fort on the winter break. He can...

Since 2 snowballs are melting every 15 minutes, we'll
compute how many snowballs does Justin really make in an
hour.

Since 1 hour = 60 minutes = 4*15 minutes, the number
of snowballs melt in an hour is = 4*2 = 8 melted
snowballs.

We'll subtract 8 snowballs from the total
numbers,15, of snowballs made in an hour.

The number of
snowballs from an hour = 15 - 8 = 7snowballs/hour

Now,
we'll apply the rule of three:

7
snowballs..................................1 hour

210
snowballs...............................x hours

We'll cross
multiply:

x =
210/7

x = 30 hours for making 210
snowballs.