Lesson 2.2-2.3 Adding and Subtracting Integers Essential Question: How do you add and subtract integers?
Before we start… On Monday, you had $20 in your wallet. Tuesday you went to the movies and spent $10. Wednesday you babysat and earned $25. Thursday you went out to eat with your friends and spent $15. How much do you have in your wallet on Friday?
What are integers? The numbers …, −4, −3, −2, −1, 0, 1, 2, 3, 4, … The whole numbers, their opposites and 0
How do you add and subtract integers? Same Signs Add the absolute values and keep the sign Different Signs Subtract the lesser absolute value from the greater absolute value and keep the sign of the integer with the greater absolute value If you subtract a negative number, you turn it into an addition problem.
10+14 −7+ −5 −11+6 13+ −9
−8+8 −3−12 7−9 15−8
−13+15 0+ −7 −9+6 2−7
−2−1 12− −9 15− −3 7+31
4−6 5−1 −6− −10 −3−8
Addition Properties Addition Properties Identity Property of Addition Words The sum of a number and the additive identity, 0, is the number. Numbers −6+0=−6 Algebra 𝑎+0=𝑎 Inverse Property of Addition Words The sum of a number and its additive inverse, or opposite, is 0. Numbers 5+ −5 =0 Algebra 𝑎+ −𝑎 =0
−7+7 + −8 + −5
−15+0+ −102
−36+ −26 +56
School Fair Your class has a fair to raise money for a field trip School Fair Your class has a fair to raise money for a field trip. The table shows the incomes and expenses for the fair. How much money was raised? Games $750 Display tables $625 Donations $36 Advertising -$16 Decorations -$60 Game rentals -$500
Bank Account The table shows amounts of money that Shannon deposited and withdrew from her bank account. What is the overall amount of deposit or withdrawal? Deposit $400 $125 Rent -$300 $50 Electricity Bill -$75
Fisherman A fisherman has a baited hook 5 feet below the surface of the water. He does not catch any fish, so he lowers the hook 8 feet. He catches no fish there, so he raises the level of the hook 4 feet. How deep is the hook at this point?
Bills Sarah owes $320 for the rent on her apartment Bills Sarah owes $320 for the rent on her apartment. She also owes $45 for her electric bill and $57 for her phone bill. Her paycheck for this week is $415. Will her paycheck be enough to pay the bills? How much will be left over or how much will she still need?
Temperature One day in Fairbanks, Alaska, the temperature is −15°F Temperature One day in Fairbanks, Alaska, the temperature is −15°F. During the night, the temperature drops by 16°F. How cold does it get?
Checking Account Because of a mistake in balancing her checkbook, Cora had a checking account balance of −$27. Cora did not realize this and wrote another check for $34. What is her balance now?
How do you add and subtract integers?
Ticket Out the Door −12+8− −3