Integers are subtracted in the same fashion as whole numbers, except that certain rules should be applied.
- If you subtract negative integer from positive then just add numbers ignoring any minuses, i.e a−(−b)=a+b.
- If you subtract positive integer from negative, add numbers ignoring any minuses and then place minus in front of result, i.e. −a−b=−(a+b).
Example 1. Find 46−(−21).
46−(−21)=46+21=67.
So, 46−(−21)=67 .
Next example.
Example 2. Find −35−21.
−35−21=−(35+21)=−56.
So, −35−21=−56.
- If you subtract positive integer from positive, then you are actually subtracting whole numbers.
- If you subtract two negative numbers use following rule: −a−(−b)=−a+b=b−a.
Example 3. Find 23−51.
23−51=−28.
Another example.
Example 4. Find −48−(−19).
−48−(−19)=−48+19=19−48=−29.
So, −48−(−19)=−29 .
Final example shows how to subtract more than two integers.
Example 5. Find −48−(−45)−34.
We do such problems step-by-step.
First find −48−(−45). −48−(−45)=−48+45=−3.
Now we are left with −3−34. −3−34=−(3+34)=−37.
So, −48−(−45)−34=−37.
Now, it's your turn. Take pen and paper and solve following problems.
Exercise 1. Find 36-(-21).
Answer: 57.
Exercise 2. Find -57-60.
Answer: -117.
Exercise 3. Find 100-69.
Answer: 31.
Exercise 4. Find -45-(-60).
Answer: 15.
Exercise 5. Find 65-(-34)-(-35)-21-(-45)-100.
Answer: 58.
