Swimming 79054

One hundred seventy-one pupils from the second to fourth years of primary school participated in swimming training. How many of them were from the fourth grade if there were 10% more third graders than second graders and 20% more fourth graders than third graders?

Correct answer:

d =  66

Step-by-step explanation:

r1=100%+10%=1+10010=1.1 r2=100%+20%=1+10020=1.2  b+c+d=171 c=r1 b d=r2 c  (c/r1)+(d/r2)+d=171  ((d/r2)/r1)+(d/r2)+d=171 ((d/1.2)/1.1)+(d/1.2)+d=171  2.590909d=171  d=2.59090909171=66  d=66



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