IWCF UK Branch Distance Learning Programme DRILLING CALCULATIONS

Part 1 Section 3 31 of 211

Checking using estimating

You should always make a rough estimate of your calculation when using a calculator.

For example:

Rough estimate: 785 + 87 + 101+ 90 + 100 = 990

Accurate calculation: 785 + 87 + 101 = 973

The rough estimate shows that the answer is sensible i.e. that you havent put in 1,001 instead of 101.

Try some yourself Exercise 1.9

1. Estimate the answers to the following;

a. 145 + 2,035 b. 5,763 + 12 + 300 c. 389,917 + 188,709 + 45,101 + 7 d. 23 + 196 e. 448 + 21 f. 119,987 + 219,998 + 503,945 + 754,730

2. Now calculate manually;

a. 145 + 2,035 b. 5,763 + 12 + 300 c. 389,917 + 188,709 + 45,101 + 7 d. 23 + 196 e. 448 + 21 f. 119,987 + 219,998 + 503,945 + 754,730

3. Now confirm using your calculator;

a. 145 + 2,035 b. 5,763 + 12 + 300 c. 389,917 + 188,709 + 45,101 + 7 d. 23 + 196 e. 448 + 21 f. 119,987 + 219,998 + 503,945 + 754,730

IWCF UK Branch Distance Learning Programme DRILLING CALCULATIONS

Part 1 Section 3 32 of 211

3.3 Subtraction This is concerned with taking things away.

The symbol we use is -, for example 3 1 = 2.

Example

The five drinks that you bought before costs you 10.77. You give the barman 15 then you take away the 10.77 to calculate how much change you should have.

.

(4.23 is the difference between 15 and 10.77)

15 10.77- = 4.23

Example

The eleven sacks of mud chemicals added to the drilling mud previously were removed from a pallet holding 30 sacks.

How many sacks are left?

30 - 11 = 19