Q. A chemist has one solution which is 50% acid and a second which is 25% acid. How much of each should be mixed to make 10 litres of a 40% acid solution?
(A) 4 litres of 50% and 6 litres of 25% (B) 3 litres of 50% and 7 litres of 25% (C) 6 litres of 50% and 4 litres of 25% (D) 7 litres of 50% and 3 litres of 25%
Question from Odisha OCS Paper 2 2024
The correct answer is (C) 6 litres of 50% and 4 litres of 25%
Explanation:
To solve this problem, we use the concept of mixture and alligation. Let’s break it down step by step:
Step 1: Define the variables Let the amount of the 50% acid solution be x litres. Then, the amount of the 25% acid solution will be (10 – x) litres, since the total mixture is 10 litres.
Step 2: Write the equation for the total acid content The total acid content in the mixture is given by: (Acid from 50% solution) + (Acid from 25% solution) = (Acid in 40% solution).
This can be written as: 0.50x + 0.25(10 – x) = 0.40(10)
Step 3: Simplify the equation Expand and simplify: 0.50x + 2.5 – 0.25x = 4 0.25x + 2.5 = 4 0.25x = 4 – 2.5 0.25x = 1.5 x = 1.5 ÷ 0.25 x = 6
Step 4: Interpret the result The amount of the 50% acid solution is 6 litres. The amount of the 25% acid solution is 10 – 6 = 4 litres.
Final Answer: The correct option is (C) 6 litres of 50% and 4 litres of 25%.
To solve this, we need to compare the given fractions: -8/5, -3/2, and -19/11. Since all the numbers are negative, the smaller the absolute value, the greater the number.
Step 1: Convert all fractions to decimals -8/5 = -1.6 -3/2 = -1.5 -19/11 = -1.727 (approximately)
Step 2: Compare the decimals From least to greatest: The smallest number is -19/11 (-1.727). The next smallest is -8/5 (-1.6). The largest is -3/2 (-1.5).
Step 3: Write the order From least to greatest: -19/11 < -8/5 < -3/2
Final Answer: The correct option is (C) -19/11 < -8/5 < -3/2.
Q. The probability of getting a bad egg in a lot of 400 eggs is 0.035. The number of bad eggs in the lot is
(A) 7 (B) 14 (C) 21 (D) 28
Question from Odisha OCS Paper 2 2024
The correct answer is (B) 14.
Explanation:
To solve this problem, let’s break it down step by step:
Step 1: Understand the given data The probability of getting a bad egg is 0.035. The total number of eggs in the lot is 400.
Step 2: Calculate the expected number of bad eggs The expected number of bad eggs can be calculated as: Number of bad eggs = Probability of a bad egg × Total number of eggs Number of bad eggs = 0.035 × 400 = 14.
Step 1: Determine Sonia’s work rate Sonia can copy 50 pages in 10 hours. So, Sonia’s work rate is: Work rate of Sonia = 50 pages ÷ 10 hours = 5 pages per hour.
Step 2: Determine the combined work rate of Sonia and Priya Sonia and Priya together can copy 300 pages in 40 hours. So, their combined work rate is: Combined work rate = 300 pages ÷ 40 hours = 7.5 pages per hour.
Step 3: Determine Priya’s work rate The combined work rate of Sonia and Priya is 7.5 pages per hour, and Sonia’s work rate is 5 pages per hour. Thus, Priya’s work rate = Combined work rate – Sonia’s work rate = 7.5 – 5 = 2.5 pages per hour.
Step 4: Time taken by Priya to copy 30 pages If Priya’s work rate is 2.5 pages per hour, the time taken by Priya to copy 30 pages is: Time = Work ÷ Work rate = 30 ÷ 2.5 = 12 hours.
Q. A can do 3/4 of a work in 12 days. He can complete 1/8 of the work in
(A) 3 days (B) 4 days (C) 72 days (D) 2 days
Question from Odisha OCS Paper 2 2024
The correct answer is (D) 2 days.
Explanation:
Step 1: Determine A’s work rate A can complete 3/4 of the work in 12 days. So, the amount of work A does in 1 day is: Work rate = (3/4) ÷ 12 = (3/4) × (1/12) = 1/16 of the work per day.
Step 2: Time to complete 1/8 of the work Now, we need to find how many days A will take to complete 1/8 of the work. If A completes 1/16 of the work in 1 day, then the time required to complete 1/8 of the work is: Time = (Work) ÷ (Work rate) = (1/8) ÷ (1/16) = 2 days.
Q. Find the next number in the sequence 17, 17, 51, 255, 1785
(A) 16065 (B) 19635 (C) 15965 (D) 14955
Question from Odisha OCS Paper 2 2024
The correct answer is (A) 16065
Explanation:
To determine the next number in the sequence 17, 17, 51, 255, 1785, let’s analyze the pattern:
1. First to Second Term: 17 to 17 is multiplied by 1. 2. Second to Third Term: 17 × 3 = 51. 3. Third to Fourth Term: 51 × 5 = 255. 4. Fourth to Fifth Term: 255 × 7 = 1785.
Observing the pattern, the multipliers are consecutive odd numbers: 1, 3, 5, 7. Following this pattern, the next multiplier should be 9.
Q. A sum of ₹ 10,000 is divided into two parts such that one part is invested at 8% per annum and the other at 6% per annum. If the annual interest earned from both investments is ₹ 700, what is the amount invested at 8%?
(A) ₹ 4,000 (B) ₹ 3,000 (C) ₹ 5,000 (D) ₹ 6,000
Question from Odisha OCS Paper 2 2024
The correct answer is (C) ₹5,000
Explanation:
Let’s solve this step by step.
1) Let’s say the amount invested at 8% is x Then amount invested at 6% = (10,000 – x)
2) Given that total interest = ₹700 Interest from 8% investment = 8% of x = 0.08x Interest from 6% investment = 6% of (10,000 – x) = 0.06(10,000 – x)
3) We can write the equation: 0.08x + 0.06(10,000 – x) = 700
4) Simplify right side of equation: 0.08x + 600 – 0.06x = 700
5) Combine like terms: 0.02x + 600 = 700 0.02x = 100 x = 5,000
6) Verification: Amount at 8%: ₹5,000 → Interest = ₹400 Amount at 6%: ₹5,000 → Interest = ₹300 Total interest = ₹700 ✓