Subtraction Using Compensation

To make their board game come to life, Mr. Squeaks invented a machine to teleport himself and Imani into Land O'Sweets! They land on the island in Lilly's Lolly Lake and notice a sign! : "Like lollie's, life can be sweet, solve this problem for a very nice treat!" While Mr. Squeaks and Imani try to win the game, let's help them learn about "subtraction using compensation". One way to solve subtraction equations is called compensation. Compensation is something given in return for something, in math we use this with numbers. It can be a helpful strategy to add or subtract because it makes the numbers friendlier, or, easier to subtract. When subtracting using compensation... Start by adding or subtracting to make one of the numbers friendlier. Whatever you do on one side you must do to the other side as well. Mr. Squeaks and Imani need to solve twenty-four minus fifteen to get a sweet treat from Lilly! When using compensation, first choose which number to make friendlier. Here, we can take fifteen and add five (...) to make it twenty. Since we added five to fifteen, we MUST add five to twenty-four. What is twenty-four plus five? (...) twenty-nine! Next, create a new equation using the new numbers. Our new equation is twenty-nine minus twenty. Finally, solve the new equation using a tool or strategy that works for you. Here, we can count back by tens! What is twenty-nine minus twenty? (...) Nine! That means twenty-four minus fifteen ALSO equals nine. : "Look Imani, a boat! Our sweet treat is a ride to the next challenge!" Mr. Squeaks and Imani have made it to Minty's Mansion! But, in order to unlock the gate and go through they must solve another problem! Let's use subtraction with compensation to help them. They need to solve thirty-three minus eighteen. Remember, start by choosing which number to make friendlier. Here we can add two (...) to thirty-three to make it thirty-five. Since we added two (...) to thirty-three, we MUST add two to eighteen to make it twenty. Next, create a new equation using the new numbers. Our new equation is thirty-five minus twenty. Finally, solve by counting back by tens! What is thirty-five minus twenty? (...) fifteen! That means thirty-three minus eighteen ALSO equals fifteen. : "We did it! We got the gate opened!" : "What is that sign over there though? Secret passage... is it... a shortcut?" : "If a secret tunnel is what you need, solve this problem to find some speed." How can Mr. Squeaks and Imani use compensation to solve forty-eight minus twenty-two? (...) Start by adding or subtracting to make one of the numbers friendlier. Here we can add two (...) to forty-eight to make it fifty. Since we added two (...) to forty-eight we MUST add two to twenty-two to make it twenty-four! Next, create a new equation with the new numbers. Our new equation is fifty minus twenty-six. Finally, solve by counting back by fives! What is fifty minus twenty-four? (...) twenty-six! Before we see if Mr. Squeaks and Imani won the game, let's review! When using compensation in subtraction... First choose which number to make friendlier. Whatever you do to one number MUST be done to the other. Next, create a new equation using the new numbers. Finally, solve the new equation using a tool or strategy that works for you. Now, let's see if they won! : "We did it, Imani! Let's go home!" : "That was fun but I'm glad to be home!" Mr. Squeaks]: "It sure was SWEET!"