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Find two numbers such that the mean proportional between them is `14` and third proportional to them is `112`.

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To find two numbers such that the mean proportional between them is 14 and the third proportional to them is 112, we can follow these steps: ### Step 1: Define the Variables Let the two numbers be \( A \) and \( B \). ### Step 2: Use the Mean Proportional Condition The mean proportional between \( A \) and \( B \) is given as 14. According to the definition of mean proportion, we have: \[ \frac{A}{14} = \frac{14}{B} \] Cross-multiplying gives us: \[ AB = 14 \times 14 \] Calculating the right-hand side: \[ AB = 196 \] This is our first equation: \[ (1) \quad AB = 196 \] ### Step 3: Use the Third Proportional Condition The third proportional to \( A \) and \( B \) is given as 112. According to the definition of third proportional, we have: \[ \frac{A}{B} = \frac{B}{112} \] Cross-multiplying gives us: \[ B^2 = 112A \] This is our second equation: \[ (2) \quad B^2 = 112A \] ### Step 4: Substitute for A From equation (1), we can express \( A \) in terms of \( B \): \[ A = \frac{196}{B} \] Now, substitute this expression for \( A \) into equation (2): \[ B^2 = 112 \left(\frac{196}{B}\right) \] This simplifies to: \[ B^2 = \frac{112 \times 196}{B} \] Cross-multiplying gives: \[ B^3 = 112 \times 196 \] ### Step 5: Calculate \( B \) Now we need to calculate \( 112 \times 196 \): \[ 112 \times 196 = 112 \times (14 \times 14) = (112 \times 14) \times 14 \] Calculating \( 112 \times 14 \): \[ 112 \times 14 = 1568 \] Thus: \[ B^3 = 1568 \] ### Step 6: Factorize and Solve for B We can factor \( 1568 \): \[ 1568 = 14^3 \times 2^3 \] Taking the cube root: \[ B = 28 \] ### Step 7: Calculate A Now substitute \( B \) back into equation (1) to find \( A \): \[ A \times 28 = 196 \] Thus: \[ A = \frac{196}{28} = 7 \] ### Conclusion The two numbers are: \[ A = 7 \quad \text{and} \quad B = 28 \]
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ICSE-RATIO AND PROPORTION (INCLUDING PROPERTIES AND USES)-Exercise 7(D)
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  3. Find two numbers such that the mean proportional between them is 14 an...

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  4. If x and y be unequal and x : y is the duplicate ratio of x + z and y ...

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  5. If x = (2ab)/(a + b), find the value of : (x + a)/(x - a) + (x + b)/(x...

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  6. If (4a + 9b) (4c - 9d) = (4a - 9b) (4c + 9d), prove that : a : b = c :...

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  7. If (a)/(b) = (c)/(d), show that : (a + b) : (c + d) = sqrt(a^(2) + b^...

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  8. There are 36 members in a student council in a school and the ratio of...

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  9. If 7x - 15y = 4x + y, find the value of x: y. Hence, use componendo an...

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  10. If (4m + 3n)/(4m - 3n) = (7)/(4) use properties of proportion to find ...

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  11. If x, y, z are in continued proportion, prove that : ((x + y)^(2))/((y...

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  12. Given x = (sqrt(a^(2) + b^(2)) + sqrt(a^(2) - b^(2)))/(sqrt(a^(2) + b...

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  13. If (x^(2) + y^(2))/(x^(2) - y^(2)) = 2(1)/(8), find : (i) (x)/(y)...

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  14. Using componendo and dividendo, find the value of x if (sqrt(3x+4)+sqr...

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  15. If x=(sqrt(a+1)+sqrt(a-1))/(sqrt(a+1)-sqrt(a-1)), using properties of ...

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  16. Given (x^(3)+12x)/(6x^(2)+8)=(y^(3)+27y)/(9y^(2)+27). Using componendo...

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  17. If x/(a)=y/(b)=z/(c) show that x^(3)/(a^(3))+y^(3)/(b^(3))+z^(3)/(c^(3...

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  18. If b is the mean proportion between a and c, show that : (a^(4)+a^(2...

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  19. If (7m+2n)/(7m-2n)=5/(3) use properties of proportion to find (i) m...

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  20. (i) If x and y both are positive and (2x^(2) - 5y^(2)) : xy = 1 : 3, f...

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