Question

3.) Karen stacks three boards on top of one another. The first board is 1/3 inch thick. The second board is 1/2 inch thick. The third board is 3/4 inch

thick. What is the total thickness, in inches, of all three boards?

Answer 1

13/12 inches

Explanation:

To add fractions with different denominators you must find the LCM (lowest common multiple). In this case that would be 12 since it is the lowest number divisible by 4, 3, and 2.

The numerators will all by multiplied by as much as the denominators.

For the fraction 1/3:

3 x 4 = 12

so 1 must be multiplied by 4 to give the new fraction 4/12

For the fraction 1/4:

4 x 3 = 12

so 1 must be multiplied by 3 to give the new fraction 3/12

For the fraction 1/2:

2 x 6 = 12

so 1 must be multiplied by 6 to give the new fraction 6/12

Note that the value of the fractions remain the same, the numbers are only increasing so that they can be added easily

Now add together the numerators of the fractions:

3 + 4 + 6 = 13

Therefore the total thickness is 13/12 inches.