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B6. Average (औसत)

Mean • Combined average • Changes

Chapter Overview (English + हिंदी)

Average = sum/number. SSC GD often asks combined average or effect of adding/removing a term.

औसत = कुल योग / संख्या। Combined average और add/remove effect SSC GD में common है।

Professor Tip: पहले formula याद, फिर 5 सवाल speed से, फिर 1-2 सवाल deep समझ से.

Important Formulas / महत्वपूर्ण सूत्र

Average = Sum / n
Sum = Average × n
Combined average = (n1×a1 + n2×a2)/(n1+n2)

Quick Tricks / त्वरित ट्रिक्स

  • Sum=avg×n हमेशा पहले निकालो.
  • Combined average weighted होता है.
  • One value change ⇒ sum changes.

Practice MCQs (6) – Answer Hidden by Default

Click “Show Answer” for each question. (SSC GD level)

Q1. Average of 12, 18, 20 is:
12, 18, 20 का औसत:
Answer: B (16.67) ≈ 17
Explanation: Sum=50, avg=50/3=16.67.
Trick: Sum first.
Q2. If average of 5 numbers is 24, their sum is:
5 संख्याओं का औसत 24 है। योग:
Answer: A (120)
Explanation: Sum=24×5=120.
Trick: avg×n
Q3. Average of 10 students is 50. One student leaves, average becomes 49. New student's marks:
10 छात्रों का औसत 50। 1 चला गया, औसत 49। छोड़े छात्र के अंक:
Answer: D (59)
Explanation: Old sum=500. New sum=49×9=441. Left student's marks=500−441=59.
Trick: Sum difference.
Q4. Average of 8 numbers is 15. If one number 7 is replaced by 23, new average:
8 संख्याओं का औसत 15। 7 की जगह 23। नया औसत:
Answer: B (17)?
Explanation: Old sum=120. New sum=120−7+23=136. New avg=136/8=17.
Trick: Sum changes by +16.
Q5. Average of 4 numbers is 10. Average of another 6 numbers is 20. Combined average:
4 का औसत 10, 6 का औसत 20। संयुक्त औसत:
Answer: B (16)
Explanation: Combined=(4×10+6×20)/10=(40+120)/10=16.
Trick: Weighted average.
Q6. If average of x, x+2, x+4 is 18, x=?
x, x+2, x+4 का औसत 18। x=?
Answer: B (16)
Explanation: For x, x+2, x+4 (AP), average equals middle term x+2. So x+2=18 ⇒ x=16.
Trick: AP में average = middle term.
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