Exercise 31 Page 120

Consider that we have 150 dollars in a saving account and some cash. The given tape diagram represents the ratio of our amounts of money.

According to the diagram, two parts are equal to 150 dollars. Notice that if we divide 150 by 2 we will get 75, which means that each part of the tape diagram represents 75 dollars. Since there are five parts for cash, we can multiply 75 by 5 to find our initial amount of cash. 75* 5 = 375 dollars We want to calculate the amount of cash we should deposit to have twice the amount of money in our saving account as we have in cash. To do so, let's suppose that we will subtract x dollars from the cash and added it to the saving account. Saving account&= 150 +x Cash&= 375 -x Since we want twice of money in our saving account as we have in cash, we can equate the amount of money of saving account and the double of the cash. 150 +x = 2(375-x) We will solve this equation for x to obtain the amount of money that we need to deposit into our saving account.

Therefore, we need to deposit 200 dollars into our saving account to obtain twice the amount of money as we have in cash.