The table below shows the average diameter of a pupil in a person’s
eye as he or she grows older.
age average pupil
(years) diameter (mm)
20 4.7
30 4.3
40 3.9
50 3.5
60 3.1
70 2.7
80 2.3
what is the average rate of change, in millimeters per year, of a
person’s pupil diameter from age 20 to age 80?
(1) 2.4 (3) -2.4
(2) 0.04 (4) -0.04

step by step resolutions

1) n+n+1+n+2=51

3n+3=51

3n=48

n=16

the three numbers are 16, 17 and 18.

2) x+15=4x

3x=15

x=5

radha is now 5 years old

3) the two digits are x and y.

y=3x

(10x+y)+(10y+x)=88

y=3x

11x+11y=88

y=3x

x+y=8

x+3x=8

x=2

the original number can be either 28 or 82.

4) n+(n+2)+(n+4)=48

3n+6=48

3n=42

n=14

the numbers are 14, 16 and 18.

5) y=x+3

10y+x+10x+y=143

y=x+3

11x+11y=143

y=x+3

x+y=13

x+x+3=13

2x=10

x=5

the original number can be 57 or 75.

hope this !