# math

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1) If the number 1,1/3,1/9, are terms of Geometric progression. Find its common ratio
2) If the second term of Geometric progression is equal to 3, and the 5th term is equal to 81/8. Find the 7th term.
3)If x,y,3 is a Geometric progression. Find the value of x and y
4) Insert 4 numbers between 128 and 4 to form a Geometric progression
5) The average maximum temperature in Cairo town in 1999 was 40 degree C in June, 30 degree C in July, 25.6 degree C in August and it is continue to decrease in the same manner during the following months. what will the average maximum temperature of Cairo be in February 2000 AD {(0.8)to the power of eight 0.168)

• math - ,

1.
r = 2nd/1st or 3rd/2nd
= (1/3) / 1 or (1/9) / (1/3)
= 1/3 for both

2.
ar = 3
ar^4 = 81/8
divide the second equation by the first
r^3 = 27/8
r = 3/2
take it from there

3. to be a GS
y/x = 3/y
y^2 = 3x
that's all you can do, unless you know either x or y

4.
128 , 128r , 128r^2 , 128r^3 , 128r^4 , 4

then 128r/128 = 4/(128r^4)
solve for r

5. you try it, it's easy.

• math - ,

giyfif

• math - ,

The numbers 27;x;y are in geometric progression if the sum of these numbers is 21 calculate the possible value of x and y