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Question

A family has several children. Each boy in this family has as many sisters as brothers, but each girl has twice as many brothers as sisters. How many brothers and sisters are there?

The correct answer is

4 and 3

Solving the Family Math Puzzle

This problem involves figuring out the number of boys and girls in a family based on clues about their siblings. We can solve this using algebra.

Setting Up the Variables

Let's define:

  • B = the total number of boys in the family.
  • G = the total number of girls in the family.

Analyzing the Clues

We are given two main conditions:

  1. From a boy's perspective: "Each boy in this family has as many sisters as brothers."
    • When a boy counts his siblings, he doesn't count himself.
    • Number of brothers he has = B - 1
    • Number of sisters he has = G
    • So, the equation is: B - 1 = G
  2. From a girl's perspective: "each girl has twice as many brothers as sisters."
    • When a girl counts her siblings, she doesn't count herself.
    • Number of brothers she has = B
    • Number of sisters she has = G - 1
    • So, the equation is: B = 2 * (G - 1)

Solving the Equations

Now we have a system of two equations:

  1. G = B - 1
  2. B = 2(G - 1)

We can use substitution to solve for B and G. Let's substitute the first equation into the second one:

Substitute G from equation (1) into equation (2):

B = 2((B - 1) - 1)

Simplify the expression inside the parentheses:

B = 2(B - 2)

Distribute the 2:

B = 2B - 4

To solve for B, let's rearrange the equation:

Subtract B from both sides:

0 = B - 4

Add 4 to both sides:

B = 4

So, there are 4 boys in the family.

Now, let's find the number of girls using the first equation (G = B - 1):

G = 4 - 1

G = 3

So, there are 3 girls in the family.

Verifying the Solution

Let's check if our numbers (4 boys, 3 girls) satisfy the original conditions:

  • Check condition 1 (Boy's perspective): A boy has 4 - 1 = 3 brothers and 3 sisters. Does he have as many sisters as brothers? Yes, 3 = 3.
  • Check condition 2 (Girl's perspective): A girl has 4 brothers and 3 - 1 = 2 sisters. Does she have twice as many brothers as sisters? Yes, 4 = 2 * 2.

Both conditions are met.

Final Answer

The family has 4 boys (brothers) and 3 girls (sisters).

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Important Questions from Member of a Group

  1. Find the ODD one out from the given options.

  2. Select the option that is related to the fifth word in the same way as the second word is related to the first word and the fourth word is related to the third word.

    Year : Month :: Week : Day :: Minute : ?

  3. Find the alternative that can be a member of the given group/class.

    Lock, Block, Fasten

  4. Four words have been given out of which three are alike in same manner, while one is different, Choose the odd one.

  5. Find the odd letter group

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