Problem number 21. Tim and Tom built a sandcastle and decorated it with a flag. They stuck half of the flagpole into the highest point of the castle. The upper tip of the flagpole was 80 cm above the ground and the lower tip was 20 cm above the ground. How tall was the sandcastle? a. 40 cm b. 45 cm c. 50 cm d. 55 cm e. 60 cm The measurement that we're looking for, how tall the sandcastle is, will be a sum of the 20 cm that it is from the ground to the bottom of the flagpole plus half the length of the flagpole because we know that half the flagpole is stuck into the sandcastle. We can use the numbers given in the problem to find these measurements. Since we know how far it is from the ground to the tip of the flagpole and also from the ground to the bottom tip of the flagpole, we can subtract those two numbers in order to get the height of the flagpole. 80 minus 20 gives us 60. So the flagpole is 60 cm tall. We know that exactly half the flagpole is inside the sandcastle. 60 divided by 2 is 30. So half the flagpole is 30 cm tall. Now we have the two measurements that we need to add together to get the distance that we're looking for. 30 cm plus 20 cm is 50 cm. This distance is 50 cm. This is answer C.

sandcastle

flagpole

measurement

height

calculation