3rd Grade Area of Shaded Parts Worksheet: Subtract the Gaps

Some shapes are not full rectangles. This 3rd grade area of shaded parts worksheet shows six rectangles on a grid, and each one has a few white squares. Your child finds the area of the shaded part only, and a worked example at the top of the page shows the method step by step. First, find the area of the whole rectangle. Then take away the white squares. The rectangles are small, from 16 to 28 square units, so the subtraction stays easy, even for a child who still counts on fingers. Page two is the answer key, and it shows every step. As a result, you can check the working, not only the final number.

The six answers, checked one by one

We checked all six answers on the key, and they are right. Box a is 20 minus 4, so 16. Box b is 21 minus 3, which gives 18. Box c is a frame: 25 squares minus the 9 white ones in the middle, so 16. Box d gives 11 and box e gives 10. Box f is 28 minus 10, so 18.

Two small things, though. On the key, box f skips the line 7 × 4 = 28, so show your child where that number comes from. Also, the example says "1 square units". Of course, it should say 1 square unit.

At the table: whole, white, then shaded

Read the example together first. It has three steps. First, find the area of the whole rectangle with length times width. Next, count the white squares. Finally, take them away. Your child can also count the shaded squares one by one. Both ways should give the same number.

Box c is the tricky one, because the white squares sit in the middle. Similarly, box d is only 2 rows high, so your child may count the white squares in one row and forget the other. Finding area by multiplying side lengths is part of the grade 3 measurement standard, so this page is right on level.

After the page: shade your own

Draw a rectangle of 4 by 5 on squared paper. After that, shade all but a few squares, leave the rest white, and ask your child to find the area of the shaded part. Next, swap roles. Your child shades the squares and you answer, and sometimes you make a small mistake on purpose so they can catch it. Finally, ask which way felt faster: counting the shaded squares or subtracting the white ones.