Question

the ages of A and B are in ratio5:7. Four years from now the ratio of their ages will be 3:4 The present of b is?
with explanation ​

Answer 1

Step-by-step explanation:

please mark as brainliest

Answer 2

Given :

• Ratio of ages of A and B is 5 : 7.
• Four years from now the ratio of their ages will be 3 : 4.

To Find :

Present ages of B.

Solution :

Analysis :

Here we have to take a common ratio. Considering that ratio and forming equation we can find the ages.

Explanation :

Let the common ratio be “x”.

• Age of A = 5x
• Age of B = 7x

Four years later,

• A = (5x + 4) years
• B = (7x + 4) years

It is said that four years from now the ratio of their ages will be 3 : 4.

☯ According to the question,

⇒ (5x + 4)/(7x + 4) = 3/4

By cross multiplying,

⇒ 4(5x + 4) = 3(7x + 4)

Expanding the brackets,

⇒ 20x + 16 = 21x + 12

Transposing 12 to LHS and 20x to RHS,

⇒ 16 - 12 = 21x - 20x

⇒ 4 = x

∴ x = 4.

The ages :

• A = 5x = 5 × 4 = 20 years
• B = 7x = 7 × 4 = 28 years

Present age of B is 28 years.

Verification :

LHS :

⇒ (5x + 4)/(7x + 4)

• Putting x = 4,

⇒ (5(4) + 4)/(7(4) + 4)

⇒ (20 + 4)/(28 + 4)

⇒ 24/32

Dividing both the numerator and denominator by 8,

⇒ 3/4

∴ 3/4

RHS :

∴ 3/4

∴ LHS = RHS.

• Hence verified.