To calculate the largest share, first we need to find out how much each part that makes up a share is worth.
To find out how much the smallest part is (i.e 1 part), we divide the value £400 by the sum of the shares (1+2+5) = 8,
400/8 = 50, therefore each part is £50.
to find the largest share (5) we multiply £50 by 5;
£50*5 = £250
to double check we can calculate the value of the remaining shares (2 &1) and then add them together to check it equals £400.
£502 = £100 and £501 = £50,
the sum of £250,£100 and £50 is £400 therefore we know that we have calcuated correctly