** Definition of Compatible Number **

- The word "compatible" means "well-matched". So, compatible numbers are numbers that are friendly with each other.
For example, 15 and 5 are compatible numbers when it comes to divison. Because, 5 divides 15 completely (3 × 5 = 15)

- Compatible numbers are used for mental computation. They are close in value to the actual numbers given in the problem.

- Compatible numbers are useful in estimating the sum, difference, product or quotient.

**Examples of Compatible Number**

Estimate 29 ÷ 6.5.

To estimate the quotient first round the numbers 29 and 6.5.

The reason for rounding these numbers is to make them easy to work with.

29 and 6.5 are not friendly with each other. So, try to find a pair of compatible numbers one of which is close to 29 and the other is near 6.5.

Here, 28,7 is the ideal pair of compatible numbers with 28 close to 29 and 6.5 close to 7.

Therefore, 29 ÷ 6.5 = 28 29 ÷ 7 = 4. Our estimate is 4. The actual quotient is 4.46. We are not for away from the actual answer.

Find the value of 61 × 5.8.

Solution:Compatible numbers for 61 and 5.8 are 60 and 6 respectively.

So, 61 × 5.8 = 60 × 6 = 360.

- Estimation
- Sum
- Product
- Difference
- Quotient
- Rounding of numbers