Basic Maths

 

  • To find the range of some numbers just take the smallest from the biggest. So range of: 2, 3, and 8 is 6.
     
  • The mode is the most popular number. It is the one that occurs the most. So mode of 3, 5, 6, 5, 5, 5 and 1 is 5.
     
  • To find the median of some numbers, just put them in order from smallest to biggest and then find the one in the middle. So median of 4, 3, 2, 1 and 5 is 1, 2, 3, 4, 5 in order with 3 in the middle so 3 is the median.
     
  • To find the mean of a set of numbers add them all up and divide by how many numbers there are. So mean of 4 and 10 is 4 + 10 which is 14 and divide by 2 so mean is 7.
     
  • To write any percentage as a decimal, just put a point in at the end and move it 2 places back. So 15% is 15· which is ·15  Put a 0 in front so the answer is 0·15.
     
  • To find 10% of anything just divide by 10. So 10% of £80 is £8 because 80 divided by 10 is 8.
     
  • To find 5% of anything you first need to get 10% and then half it. So 5% of £60 is 60 ÷10 which is 6 and then half it which is 3.
     
  • To find 15% of an amount, first find 10% by dividing by 10, then half it to get 5% and then add them together. So 15% of £80 is 80 ÷ 10 which is £8 and then half it to get 5% which is £4 and then add them together to get £12.
     
  • To change a percentage to a fraction just put it over 100.  So 23% is 23100
     
  • To add decimals line up the points and then add each column.
    So 4·35 + 2·8 becomes   4·35
    2·8
      7·15
  • To simplify a fraction just find a number that goes into the top and bottom.
    So 412 becomes 13 because 4 will divide into the top and bottom numbers once and 3 times.
     
  • A quick way of writing a x a x a is a³
     
  • When using algebra put it in real life contexts where possible.  So 2cp + 4cp could be 2 chicken pies plus 4 chicken pies which would be 6cp.
     
  • To find 2 thirds of something first find 1 third by sharing by 3 and then double it.
    So 23 of 12 is 8 because 13 is 4 so 23 would be 8.
     
  • The slow way of writing 3k is 3 x k so if k = 6 then 3k will be 18 because 3k means 3 x k.
     
  • Brackets mean times everything in the bracket by whatever is outside.  So 5(b + 4) would be 5b + 20.
     
  • Probability can only be written as a fraction, decimal or percentage. The probability of picking an ace out of a pack is: 452 because there are 4 aces and 52 cards.
     
  • 2³ means 2 x 2 x 2.
     
  • To multiply fractions just multiply the tops and then multiply the bottoms So 25 x 35 is 625
     
  • Factors of a number are numbers that go into it. So factors of 10 are 1, 2, 5 and 10.
     
  • A Prime Number is a number that only has 2 factors eg 7, 5, 11, 29 … the only factors of 7 are 7 and 1.
     
  • Multiples of a number is the times table.  So multiples of 4 are 4, 8, 12, 16, 20…..
     
  • To add and subtract negative numbers think of a thermometer. So -5 -2 would be -7.  The temperature is -5 and it falls by another 2 degrees to end up at -7
     

When plotting axes, be careful of scale and be consistent, eg

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If graph doesn't start at 0 use zigzag   to indicate this. Use x to plot points. Accuracy is vital.
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