Grade 7 | Unit 5 | Lesson 14: Solving Problems with Rational Numbers | Practice Problems

A bank charges a service fee of $7.50 per month for a checking account. A bank account has $85.00. If no money is deposited or withdrawn except the service charge, how many months until the account balance is negative?

• 10 months

• 11 months

• 12 months

• 13 months

Month	Transactions
January	-38.50, 126.30, 429.40, -265.00
February	250.00, -135.20, 35.50, -62.30
March	-14.00, 99.90, -82.70, -1.50
April	-86.80, -570.00, 100.00, -280.10

Find the total of the transactions for each month. Find the mean total for the four months.

A large aquarium of water is being filled with a hose. Due to a problem, the sensor does not start working until some time into the filling process. The sensor starts its recording at the time zero minutes. The sensor initially detects the tank has 225 liters of water in it. The hose fills the aquarium at a constant rate of 15 liters per minute. What will the sensor read at the time 5 minutes?

Later, someone wants to use the data to find the amount of water at times before the sensor started. What should the sensor have read at the time -7 minutes?

A furniture store pays a wholesale price for a mattress. Then, the store marks up the retail price to 150% of the wholesale price. Later, they put the mattress on sale for 50% off of the retail price. A customer just bought the mattress on sale and paid $1,200. What was the retail price of the mattress, before the discount?

What was the wholesale price, before the markup?