Guided Practice

You can use the Slingshot Method to think about how to subtract with negative numbers too. The image shows the difference –3 – (–6).

The starting number is –3. Subtraction always moves the marker to the left. And subtracting a negative means we slingshot. We move 6 units to the right of –3, which is positive 3. So the difference is 3.

Enter the sum.

4 + (–6) =

Enter the sum.

–2 + 3 =

Enter the sum.

–1 + (–8) =

Enter the sum.

Draw on the number line to help you.

–9 + 9 =

Enter the sum.

Draw on the number line to help you.

1 + (–7) =

Enter the sum.

Draw on the number line to help you.

–3 + (–2) =

Enter the sum.

Draw on the number line to help you.

8 + (–5) =

Enter the sum.

Draw on the number line to help you.

5 + (–4) =

Enter the sum.

Draw on the number line to help you.

–3 + (–3) =

Enter the sum.

Draw on the number line to help you.

3 + (–6) =

Enter the sum.

–25 + (–11) =

Enter the sum.

16.2 + (–8.5) =

Enter the difference.

–3 – (–6) =

Enter the difference.

Draw on the number line to help you.

1 – (–1) =

Enter the difference.

Draw on the number line to help you.

2 – (–3) =

Enter the difference.

Draw on the number line to help you.

–5 – (–3) =

Enter the difference.

Draw on the number line to help you.

0 – (–4) =

Enter the difference.

Draw on the number line to help you.

–4 – (–4) =

Enter the difference.

–100 – (–25) =

Enter the difference.

20.4 – (–3.6) =

The opposite of –3 is 3. The opposite of 3 is –3. When you add a number and its opposite, the sum is 0.
When you add a negative number, this is the same as subtracting the opposite of the number. When you subtract a negative number, this is the same as adding the opposite of the number.

3 + (–3) = 3 – 3

5 – (–7) = 5 + 7

Drag the handle to the left to subtract and to the right to add. Use the tool to determine each sum or difference.

0 – (–1) =

1 + (–5) =

–4 + (–5) =

–9 – (–3) =

–6 – (–8) =

2 + (–12) =

4 + (–4) = 4 –

4 + (–4) = 4 –

–7 – (–10) = –7 +

–7 – (–10) = –7 +

–2 – (–8) = –2 +

–2 – (–8) = –2 +

–9 + (–1) = –9 –

–9 + (–1) = –9 –

8 + (–11) = 8 –

8 + (–11) = 8 –

During one day in winter, the high temperature in Pittsburgh, Pennsylvania, was –5°F. The high temperature decreased 2°F the next day. What was the high temperature the next day?

You can subtract: –5 – 2 = –7. So the high temperature the next day was –7°F.

Write the expression –5 – 2 in a different way.

–5 – 2 = –5 + ()

A stock price showed these price changes over the course of three days: –$3, +$12, –$5. If the price of the stock started at $45, what was the price after the three days?

Complete the subtraction expression with the amounts in order and without the dollar signs. Then determine the price.

$45 – () – () – ()

Price after 3 days: $

The temperature increased from –15° to 25° over the course of 1 week. What was the total change in temperature?

Write the subtraction expression. Then solve the problem.

25 – ()

The temperature increased degrees.

Tia was $15 below her fundraising goal. Then she got a check for $40.

Complete the sentence to describe Tia's amount now. Use "above" or "below" in the sentence.

Tia is now her goal by $.

Sam had $35 in his checking account. He made a withdrawal from his account, which made the balance –$7. How much did Sam withdraw?

Complete the subtraction expression and then solve the problem.

35 – ()

Sam withdrew $.

You learned before how to solve equations like x + 4 = 10.

Subtract 4 from x + 4 and subtract 4 from 10 to see that x = 6.

Now you can solve equations by operating with negative numbers too.

Try: p – 3 = –2.

Solve the equation.

p – 3 = –2

p =

Solve the equation.

3/2+ r = 1/2 + 1/2

r =

Solve the equation.

20 = –5 – h

h =

Solve the equation.

2 + c = –8

c =

Solve the equation.

–1 – w = –8

w =

Solve the equation.

–1/2= b – 1/2

b =

Solve the equation.

5 + g = 1

g =

Solve the equation.

t – 4 = –9

t =

Solve the equation.

12 = –6 + x

x =

Solve the equation.

q – (–2) = 30

q =

Solve the equation.

100 = m + –1

m =

Solve the equation.

y + 0.5 = –3.5

y =

Solve the equation.

10.1 = 10.5 + k

k =

Solve the equation.

2 + f = –4

f =

You can use some rules to help you add and subtract with negative numbers. For example:

- Adding two positive numbers results in a positive number.
- Adding two negative numbers results in a negative number.

Try to reason about adding and subtracting on a number line as moving left and right. This will help you more in the long run than memorizing rules!

Try these.

–5 – (–5) =

–5 + (–5) =