UPSC Prelims 2022·CSAT·Quantitative Aptitude·Arithmetic

A bill for ₹1,840 is paid in the denominations of ₹50, ₹20 and ₹10 notes. 50 notes in all are used. Consider the following statements: 1. 25 notes of ₹50 are used and the remaining are in the denominations of ₹20 and ₹10. 2. 35 notes of ₹20 are used and the remaining are in the denominations of ₹50 and ₹10. 3. 20 notes of ₹10 are used and the remaining are in the denominations of ₹50 and ₹20. Which of the above statements are not correct?

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  1. A1 and 2 only
  2. B2 and 3 only
  3. C1 and 3 only
  4. D1, 2 and 3Correct

Explanation

Let N50, N20, and N10 be the number of notes of denominations ₹50, ₹20, and ₹10 respectively. Given: Total amount = 50*N50 + 20*N20 + 10*N10 = 1840 Total number of notes = N50 + N20 + N10 = 50 Let's analyze each statement: Statement 1: 25 notes of ₹50 are used (N50 = 25). Substitute N50 = 25 into the equations: 1) 50*25 + 20*N20 + 10*N10 = 1840 => 1250 + 20*N20 + 10*N10 = 1840 => 20*N20 + 10*N10 = 590 2) 25 + N20 + N10 = 50 => N20 + N10 = 25 From the second derived equation, N10 = 25 - N20. Substitute this into the first derived equation: 20*N20 + 10*(25 - N20) = 590 20*N20 + 250 - 10*N20 = 590 10*N20 = 340 N20 = 34 Now find N10: N10 = 25 - 34 = -9. Since the number of notes cannot be negative, Statement 1 is incorrect. Statement 2: 35 notes of ₹20 are used (N20 = 35). Substitute N20 = 35 into the equations: 1) 50*N50 + 20*35 + 10*N10 = 1840 => 50*N50 + 700 + 10*N10 = 1840 => 50*N50 + 10*N10 = 1140 2) N50 + 35 + N10 = 50 => N50 + N10 = 15 From the second derived equation, N10 = 15 - N50. Substitute this into the first derived equation: 50*N50 + 10*(15 - N50) = 1140 50*N50 + 150 - 10*N50 = 1140 40*N50 = 990 N50 = 990 / 40 = 24.75 Since the number of notes must be an integer, Statement 2 is incorrect. Statement 3: 20 notes of ₹10 are used (N10 = 20). Substitute N10 = 20 into the equations: 1) 50*N50 + 20*N20 + 10*20 = 1840 => 50*N50 + 20*N20 + 200 = 1840 => 50*N50 + 20*N20 = 1640 2) N50 + N20 + 20 = 50 => N50 + N20 = 30 From the second derived equation, N20 = 30 - N50. Substitute this into the first derived equation: 50*N50 + 20*(30 - N50) = 1640 50*N50 + 600 - 20*N50 = 1640 30*N50 = 1040 N50 = 1040 / 30 = 104 / 3 = 34.66... Since the number of notes must be an integer, Statement 3 is incorrect. Since all three statements (1, 2, and 3) are incorrect, the correct option is D. The final answer is D
Quantitative Aptitude: A bill for ₹1,840 is paid in the denominations of ₹50, ₹20 and ₹10 notes. 50 notes in all are used. Consider the followi

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