How to solve this Pri 6 ratio and proportion question ?

syncopation_music SG

Hi, I need help on the detailed workings how to solve this ratio and proportion question

Peter,James and Ruth had some stamps.James and Ruth together had 3 times as many stamps as Peter.The ratio of the number of stamps James had to the number of stamps Ruth had was 3:7 .Peter and Ruth had 310 stamps altogether.How many stamps did Ruth have ?

eagle SG

3:7 can be converted to 9:21

Since James and Ruth together had 3 times as many stamps as peter, the ratio of Peter:James:Ruth is

10:9:21

Peter and Ruth=> 10:21 has 310 stamps

So Ruth has 310 / 31 * 21 = 210 stamps

Regards,
Eagle
Owner of Strategic Tuition