There are 7 new books and 8 used books on a shelf. (a) what is the ratio of all books to used books? (b) what is the ratio of new books to all books?

(a) 15:8

(b) 7:15

Step-by-step explanation:

a: All the books together is 15. The ratio of all books(15) to used books(8) is therefore 15:8

b: As I said above, all the books together is 15. So the ratio of the new books(7) to all books(15) is 7:15

hello,

b) 62.47% of the students are between 14 and 18 years old.

step-by-step explanation:

mean = 15 and standard deviation = 2

student between 14 to 18

formula used z-score

for age 14 , z score

using z-table , p(z> -0.5)=0.3085

for age 18 , z score

using z-table , p(z< 1.5)=0.9332

p(-0.5< z< 1.5)=0.9332-0.3085 = 0.6247

thus, 62.47% of the students are between 14 and 18 years old.

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