NCERT Class XI Mathematics - Linear Inequalities - Solutions
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Question : 22
Total: 65
To receive Grade ‘A’ in the course, one must obtain an average of 90 marks or more in five examinations (each of 100 marks). If Sunita’s marks in first four examinations are 87, 92, 94 and 95, find minimum marks that Sunita must obtain in fifth examination to get grade ‘A’ in the course.
Solution:
Let Sunita obtained x marks in the fifth examination.
∴ Average marks of 5 examinations
=
This average must be atleast 90
∴
Multiplying both sides by 5
368 + x ≥ 5 × 90 = 450
Transposing 368 to R.H.S., we get x ≥ 450 – 368 = 82
∴ Sunita should obtain atleast 82 marks in the fifth examination.
∴ Average marks of 5 examinations
=
This average must be atleast 90
∴
Multiplying both sides by 5
368 + x ≥ 5 × 90 = 450
Transposing 368 to R.H.S., we get x ≥ 450 – 368 = 82
∴ Sunita should obtain atleast 82 marks in the fifth examination.
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