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# in a school 1620 pupils the ratio of boys to girls is 4:5. what is the nunber of girls in the school??????????

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in a school 1620 pupils the ratio of boys to girls is 4:5. what is the nunber of girls in the school??????????

Guest Oct 18, 2014

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+93664
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I quite like to do these without algebra - I'll see if I can demonstrate my method.

the black numbers are the ones you have been given.

the ratio of boys to girls is 4:5 so in total there is some multiple of 9 students altogether.

Next you have to say

$$\begin{tabular}{|c|c|c|}\hline boys & girls & Total\\\hline 4&5&{4+5=9} \\\hline & &1620\\\hline \end{tabular}$$

$$\\{1620\div 9 = 180} \quad 180 is the multiplication factor\\ so\\ number of boys is 4\times 180 = 720 \quad Put that in the box under the 4\\ and\\ number of girls is 5\times 180 = 900 \quad Put that in the box under the 5\\\\ Total number of  { \;purple\;penguins\;}  is  720+900=1620  that checks out very nicely.  \\\\ The purple penguins is an insider joke - don't worry if you don't get it - you can google it if you want, then you will know what I am talking about.$$$Melody Oct 19, 2014 #1 +17745 0 If the ratio of boys to girls is 4:5, then the ratio of girls to boys is 1:5, which is 1/5. 1/5 of 1620 = (1/5) x 1620 = 324 geno3141 Oct 18, 2014 #2 +90001 +5 If the ratio is 4:5, then 4/9 are boys and 5/9 are girls. Then....5/9 x 1620 = 900 girls And 4/9 x 1620 = 720 boys CPhill Oct 18, 2014 #3 +93664 +5 Best Answer I quite like to do these without algebra - I'll see if I can demonstrate my method. the black numbers are the ones you have been given. the ratio of boys to girls is 4:5 so in total there is some multiple of 9 students altogether. Next you have to say $$\begin{tabular}{|c|c|c|}\hline boys & girls & Total\\\hline 4&5&{4+5=9} \\\hline & &1620\\\hline \end{tabular}$$ $$\\{1620\div 9 = 180} \quad 180 is the multiplication factor\\ so\\ number of boys is 4\times 180 = 720 \quad Put that in the box under the 4\\ and\\ number of girls is 5\times 180 = 900 \quad Put that in the box under the 5\\\\ Total number of { \;purple\;penguins\;} is 720+900=1620 that checks out very nicely. \\\\ The purple penguins is an insider joke - don't worry if you don't get it - you can google it if you want, then you will know what I am talking about.$$$

Melody  Oct 19, 2014