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Average practice question for Railways, SSC. Review the correct answer and explanation, then continue with related practice below.

Question language / प्रश्न भाषा

The average of 15 numbers is 80. The average of the first 6 numbers is 72. The average of the next 6 numbers is 25% more than the average of the first 6 numbers. The 13th number is 8 more than the 15th number, and the 14th number is 10 less than the 15th number. What is the average of the 13th and 14th numbers?

15 संख्याओं का औसत 80 है। पहली 6 संख्याओं का औसत 72 है। अगली 6 संख्याओं का औसत पहली 6 संख्याओं के औसत से 25% अधिक है। 13वीं संख्या, 15वीं संख्या से 8 अधिक है और 14वीं संख्या, 15वीं संख्या से 10 कम है। 13वीं और 14वीं संख्याओं का औसत क्या है?

Answer and explanation are free to read — no sign-in required.उत्तर और व्याख्या पढ़ने के लिए साइन-इन आवश्यक नहीं है।

A

70.89

B

85

C

75.67

✓

D

80.65

Correct Answerसही उत्तर

C. 75.67

Explanationव्याख्या

Average of the next 6 numbers:
Then:
2 = x − 1 = 230
3 − 1 = 227
3 ≈ 75.67 Hence, the correct answer is 75.67.

अगली 6 संख्याओं का औसत: = 72 + 25% of 72 = 72 + 18 = 90 Net deviation of first 12 numbers from average 80:
औसत 80 से पहली 12 संख्याओं का कुल विचलन: = 6 × (72 − 80) + 6 × (90 − 80) = −48 + 60 = +12 Therefore, the sum of the 13th, 14th and 15th numbers:
अतः 13वीं, 14वीं और 15वीं संख्याओं का योग: = (3 × 80) − 12 = 228 Let the 15th number be x.
मान लें 15वीं संख्या x है।
तब: 13th number = x + 8 13वीं संख्या = x + 8 14th number = x − 10 14वीं संख्या = x − 10 Therefore: (x + 8) + (x − 10) + x = 228 3x − 2 = 228 3x = 230 x = 230
3 Average of the 13th and 14th numbers: 13वीं और 14वीं संख्याओं का औसत: = [(x + 8) + (x − 10)] ÷ 2 = (2x − 2)
अतः सही उत्तर 75.67 है।

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