Fourth proportional calculator

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Solution

Solution provided by AtoZmath.com

1. If `a:b:c=2:3:5` then find value of `(a^2+b^2+c^2)/(ab+bc+ca)`

1. If `a/b=2/3`, then find `(2a-3b)/(a-2b)`

2. If `a:2=b:3=c:5`, then find `(a^2+b^2+c^2)/(ab+bc+ca)`

3. If `a/4=b/15`, then find `(a+b)/(a-b)`

4. If `(2a+3b)/(a+b)=13/5`, then find `a/b`

5. If `(x^2+1)/(x^2-1)=2`, then find `x`

6. If `x:30=12:20`, then find `x`

2. If `a:b=2:3,b:c=4:5` then find `a:b:c`

1. If `a:b=2:3,b:c=4:5`, then find `a:b:c`

2. If `b:c=4:5,c:d=5:6`, then find `b:c:d`

3. If `a:b=2:3,b:c=4:5,c:d=5:6`, then find `a:b:c:d`

4. If `2a=3b`, then find `a:b`

5. If `2a=3b=7c`, then find `a:b:c`

3. If `a/b=c/d=e/f` then prove that `(2a+3c-4e)/(2b+3d-4f)=(5a-4c+3e)/(5b-4d+3f)`

1. If `a/b=c/d=e/f`, then prove that `(2a+3c-4e)/(2b+3d-4f)=(5a-4c+3e)/(5b-4d+3f)`

2. If `x/(b^2-c^2)=y/(c^2-a^2)=z/(a^2-b^2)`, then prove that `x+y+z=0`

4. If `x/(y+z)=y/(z+x)=z/(x+y)` then prove the value of each ratio is `1/2` or `-1`

1. If `x/(y+z)=y/(z+x)=z/(x+y)`, then prove each ratio = `1/2,-1`

2. If `(5a+6b)/(7c)=(6b+7c)/(5a)=(7c+5a)/(6b)`, then prove each ratio = `2,-1`

3. If `(ax+by)/(x+y)=(ay+bz)/(y+z)=(az+bx)/(z+x)`, then prove each ratio = `(a+b)/2`

5. Geometric Mean

1. Geometric Mean of `49/4` and `16/9`

2. Geometric Mean of `8a^2` and `32b^2`

3. Geometric Mean of `(a-b)^2` and `(a+b)^2`

4. If geometric mean `6x^2` and x is `9x`, find value of x

6. Ratios(duplicate, triplicate) and proportional(mean, third, fourth)

1. Duplicate ratio of 2:3

2. Triplicate ratio of 2:3

3. Sub-Duplicate ratio of 16:25

4. Sub-Triplicate ratio of 8:27

5. Compounded ratio of 2:5,3:4

6. Compounded ratio of 2:3,3:4,4:5

7. Mean proportional of 8,32

8. Third proportional of 16,36

9. Fourth proportional of 3,7,15

10. Compare ratios of 2:3,3:4,4:5

Example

1. Find Fourth proportional of `3,7,15`

Solution:

In `a:b :: c:d`, we say that `d` is the fourth proportional to `a,b,c`.

Let the fourth proportional to the numbers `3,7,15` be `x`.

Then, `3:7=15:x`

`:. 3/7=15/x`

`:. x = (7 xx 15)/(3)`

`:. x = 35`