The weights (in g) of packets received in a post office in one day are given below. If the modal weight of the packets is 31.6 g, then what is the value of x? 

Weight (in g) 16-22 22-28 28-34 33-40 40-46
Number of packets 13 16 25 x 20

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AAI Junior Assistant (Fire Service) Official Paper (Held On: 15 Nov 2022 Shift 1)
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  1. 19
  2. 21
  3. 17
  4. 18

Answer (Detailed Solution Below)

Option 1 : 19
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ST 1: English
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Detailed Solution

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Given:

Modal weight = 31.6 g

Formula used:

Mode = L + [(fm - f1) ÷ (2fm - f1 - f2)] × h

Where,

L = Lower boundary of modal class = 28

fm = Frequency of modal class = 25

f1 = Frequency of class before modal class = 16

f2 = Frequency of class after modal class = x

h = Class width = 6

Calculation:

31.6 = 28 + [(25 - 16) ÷ (2 × 25 - 16 - x)] × 6

⇒ 31.6 - 28 = (9 ÷ (50 - 16 - x)) × 6

⇒ 3.6 = 54 ÷ (34 - x)

⇒ 3.6 × (34 - x) = 54

⇒ 122.4 - 3.6x = 54

⇒ 68.4 = 3.6x

⇒ x = 19

∴ The correct answer is 19.

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