The diameter of a circle increased from 25cm to 25.8cm. Find the percentage increase in its circumference.

3.1% increase

Step-by-step explanation:

Diameter1=25cm

Radius1=12.5cm

Circumference1=2x22/7x12.5

Diameter2=25.8cm

Radius2=12.9cm

Circumference2=2x22/7x12.9

% increase =Circumference2-Circumference1/Circumference2 x 100%= 2x22/7x12.9-2x22/7x12.5 / 2x22/7x12.9 x100%

12.9-12.5/12.9 x 100%

0.4/12.9 x 100%

4/129 x 100%

3.1%

34

step-by-step explanation:

a 4/6 = 9/12   not proportional

step-by-step explanation:

to find which are not proportional, we can use cross products

if it is true, they are proportional.   if it is not true, they are not proportional.

a 4/6 = 9/12

4* 12 = 6*9

48 = 54

not this is not proportional  

b 2/3 = 12/18  

2* 18 = 3 * 12

36 = 36

this is proportional

c 5/4 = 10/8  

5*8 = 4*10

40 = 40

this is proportional

d 7/5 = 35/25

7*25 = 5 * 35

175 = 175

is proportional