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 build 15 snowballs/hour but two snowballs melt every...

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 build 15 snowballs/hour but two snowballs melt every 15 minutes. How long will it take him to build 210 snowballs.

Asked on by fromici

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justaguide's profile pic

justaguide | College Teacher | (Level 2) Distinguished Educator

Posted on

Justin builds 15 snowballs in an hour and 2 snowballs melt every 15 minutes.

So in an hour he makes 15 snowballs of which 2*4 = 8 melt leaving him with 7.

As he needs to build 210  snowballs, it will require 210/7 = 30 hours.

The total time required to build 210 balls is 30 hours.

giorgiana1976's profile pic

giorgiana1976 | College Teacher | (Level 3) Valedictorian

Posted on

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.

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