GPhC Exam Calculation Questions

Calculating things in your head can be a difficult task. I remember in math lessons at school the teacher would always say you need to do this in your head as in the future you will never have a calculator in your pocket all the time. I now look at my iPhone in despair, that I do. Never the less, we need to be prepared for those cataclysmic circumstance when there is no iphone and a patient needs a specific dose of a medicine.

If you you have always been reliant on technology to do the hard math for you or simply don't know how to solve a problem then mental arithmetic can be very challenging and frustrating. I'm going to try and give a few tips on how to do it more easily so you can pass the GPhC Exam. My own mental calculation skills are below my general maths ability due to problems with short term memory, but with a few shortcuts I can often calculate things scarily fast. Heres one to get you started...

Addition

A useful trick when adding lots of small numbers is to clump together the ones that add up to multiples of 10. For example, if you have to add 2 + 3 + 5 + 7 + 9 + 11 + 8, that can be rearranged as (3 + 7) + (9 + 11) + (2 + 8) + 5 = 10 + 20 + 10 + 5 = 45.

This method is also useful when performing column addition with more than two numbers. For example, in the problem:

 56

 35

 47

 21

 12

 32

+23 

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Column addition is generally performed by adding the digits in the ones place, carrying them over, and then adding the digits in the tens place., and so on. A way to make this task easier is to group the digits in the ones place in groups of ten, and mark them on your paper like this:

 5 6

 3 5

 4 7\

 2 1 \

 1 2    -- 10

 3 2  /

+2 3/ 

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Similarly the 6, 2, and 2 would be crossed off, yielding another 10. Therefore the digits in the ones place add up to 10+10+5+1 (what's left) or 26.