Bank Account Tracker

Pre-Algebra · Axiom Academy

A checking account is just signed numbers in disguise: deposits add, withdrawals subtract, and the balance is the running total — even when it drops below zero. 1. Deposits Add, Withdrawals Subtract Open your account with a balance of 100 . Two things can happen to it. A deposit adds money — a positive number. A withdrawal spends money — a negative number. Watch the balance bar take a +50 deposit up to 150 , then a −30 withdrawal back down to 120 . A deposit is a positive number A withdrawal is a negative number 2. The Balance Is a Running Total Now a real week. Start at 50 and post four transactions one at a time. After each one, your new balance is the old balance plus the signed amount . Watch the dot walk up and down a balance track as the ledger fills in row by row — the balance is a running sum , never a fresh calculation. 50 + 30 = 80 . Money in pushes the dot up. 80 − 60 = 20 . A big withdrawal drops it low. 20 − 35 = −15 . Spending past zero goes negative. −15 + 40 = 25 . A deposit climbs back above zero. You never recompute from scratch. Each step just carries the previous balance forward: . The same dot that ended one step starts the next. 3. Crossing Zero Is an Overdraft What happens when you spend more than you have? Start at 50 and withdraw 80 . The balance marker slides left along the number line, passes 0 , and lands at −30 . Below zero the line shades red — that region is an overdraft : you owe the bank money. A positive number — the account is in the black.

This is the written version of the interactive lesson above. See the full Pre-Algebra course.