In the N5 exam, you’ll be expected to do the following types of calculations:
Averages
Add up all the numbers and then divide by however many numbers you’ve added together.
Ratios
Write down each number with a : between them. Simplify each number until they can’t be simplified anymore by finding a common factor that is divisible by both numbers. If there is a decimal place, multiply each number by 10, 100 etc. to get a whole number, then simplify as normal.
Your answer must in it’s SIMPLEST form and be a WHOLE NUMBER.
Percentages
% = Number of interest (X) / Total Number x 100
Divide the number of interest (let’s call it X) by the total number (imagine you are calculating your test score % – you all know how to do that!) and times it by 100 to get a percentage.
If you are told the percentage and need to know the number of X, then divide the total number by 100 and times it by the percentage.
Number of interest (X) = Total Number/100 x %
OR change the percentage into a decimal (ie 80% is 0.8, 50% is 0.5 and 10% is 0.1) and multiply that decimal by the total number and you will get number X.
Number of interest (X) = Total Number x decimal of the %
Percentage changes (increase or decrease)
Change/Original x 100
Change = the difference in the start and end values
Original = the start/first value
Cell Size
Cell Size = Diameter / number of cells across the field of view
You may need to convert the units from mm to μm or vice versa.
1mm = 1000μm so you need to times mm by 1000 or divide a μm by 1000 to change the value for the appropriate units.
The answer will indicate the final units needed.
Scaling (how many times greater/smaller)
How many times greater/smaller = Bigger number/smaller number
Converting between units (eg seconds to minutes, or g to kg, or mm to μm)
Seconds to minutes = divide the seconds value by 60 to convert to minutes
Minutes to seconds = times the minutes value by 60 to convert to seconds
Grams (g) to Kilograms (kg) = divide the g value by 1000 to convert to kg
Kilograms (kg) to Grams (g) = times the kg value by 1000 to convert to g
Millimeters (mm) to micrometers (μm) = times the mm value by 1000 to convert to μm
Micrometers (μm) to millimeters (mm) = divide the μm value by 1000 to convert to mm
Doubling (eg when calculating cell division numbers)
You may be asked how many cells there will be if 1 cell goes through 4 divisions, or something similar.
You simply double the number of cells with each division:
1 –> 2 –> 4 –> 8 –> 16
Each doubling (arrow) represents one division. Use this method and you’ll be fine in the exam.