21 chaperones are needed for 420 students.
Step-by-step explanation:
No. of juniors = 148
No. of seniors = 272
Total = 148+272 = 420 students
3 chaperones = 60 students
1 chaperone = ![\frac{60}{3}=20\ students](https://tex.z-dn.net/?f=%5Cfrac%7B60%7D%7B3%7D%3D20%5C%20students)
Ratio of chaperon to students = 1:20
Let,
x be the number of chaperons for 420 students.
Ration of chaperones to students = x:420
Using proportion
Ratio of chaperones to students :: Ratio of chaperons to students
![1:20::x:420](https://tex.z-dn.net/?f=1%3A20%3A%3Ax%3A420)
Product of mean = Product of extreme
![20*x=420*1\\20x=420\\](https://tex.z-dn.net/?f=20%2Ax%3D420%2A1%5C%5C20x%3D420%5C%5C)
Dividing both sides by 20
![\frac{20x}{20}=\frac{420}{20}\\x=21](https://tex.z-dn.net/?f=%5Cfrac%7B20x%7D%7B20%7D%3D%5Cfrac%7B420%7D%7B20%7D%5C%5Cx%3D21)
21 chaperones are needed for 420 students.
Keywords: ratio, proportion
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