The average height of three boys is thrice height of the fourth boy. I

1.	The average height of three boys is thrice height of the fourth boy. If the average height of all boys is 165 cm, then find the height of fourth boy.1. 70 cm2. 155 cm3. 66 cm4. 150 cm
Answer» Correct Answer - Option 3 : 66 cm Given: The average height of three boys is thrice height of the fourth boy. The average height of all boys = 165 cm. Formula used: Average = (sum of total observations)/(numbers of observations) Calculation: Let the height of boys be w, x, y and z. According to the question, (w + x + y)/3 = 3z ⇒ w + x + y = 9z ----(I) Average = (sum of total observations)/(numbers of observations) ⇒ Sum of total observations = average × (numbers of observations) ⇒ w + x + y + z = 165 × 4 ⇒ 9z + z = 660 (using equation (I)) ⇒ 10z = 660 ⇒ z = 66 cm ∴ The height of fourth boy is 66 cm.

The average height of three boys is thrice height of the fourth boy. If the average height of all boys is 165 cm, then find the height of fourth boy.1. 70 cm2. 155 cm3. 66 cm4. 150 cm

Answer» Correct Answer - Option 3 : 66 cm

Given:

The average height of three boys is thrice height of the fourth boy.

The average height of all boys = 165 cm.

Formula used:

Average = (sum of total observations)/(numbers of observations)

Calculation:

Let the height of boys be w, x, y and z.

According to the question,

(w + x + y)/3 = 3z

⇒ w + x + y = 9z ----(I)

Average = (sum of total observations)/(numbers of observations)

⇒ Sum of total observations = average × (numbers of observations)

⇒ w + x + y + z = 165 × 4

⇒ 9z + z = 660 (using equation (I))

⇒ 10z = 660

⇒ z = 66 cm

∴ The height of fourth boy is 66 cm.

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