SSC CGL Mixture and Alligation Practice Test 8

1. Ratio of ages of father and son is 7:2. Sum of their ages is 54. Father's age is:

• A. 36
• B. 38
• C. 40
• D. 42 (Correct)

Explanation: Father = 54×7/9 = 42.

2. Average of 7 numbers is 28. If two numbers 30 and 34 are removed, new average:

• A. 24
• B. 26 (Correct)
• C. 27
• D. 28

Explanation: Sum=196. New sum=196−64=132. New avg=132/5=26.4≈26.

3. A:B = 3:5 and B:C = 2:3. Find A:B:C.

• A. 6:10:15 (Correct)
• B. 3:5:6
• C. 2:5:9
• D. 4:6:9

Explanation: Scale B: A:B=6:10, B:C=10:15. So A:B:C=6:10:15.

4. A jar contains milk and water in ratio 5:3. If 16 litres of mixture is removed and replaced with water, ratio becomes 3:5. Original quantity:

• A. 32 L
• B. 40 L (Correct)
• C. 48 L
• D. 64 L

Explanation: Let total=x. Milk initially=5x/8. After replacing: milk=(5x/8−10)=3x/8 → 5x/8−10=3x/8 → 2x/8=10 → x=40.

5. Mean of 10 observations is 15. One observation 20 is later found to be 25. Corrected mean:

• A. 15.5 (Correct)
• B. 16
• C. 16.5
• D. 17

Explanation: Sum=150. Corrected sum=150+5=155. Mean=155/10=15.5.

6. If A:B = 2:3 and B:C = 6:5, find A:C.

• A. 4:5 (Correct)
• B. 5:6
• C. 4:6
• D. 12:10

Explanation: A:B:C. B=3=6k → k=1/2. A:B=2:3=4:6, B:C=6:5. A:C=4:5.

7. A and B invest in ratio 4:5. A invests for 12 months, B for 8 months. Profit ratio:

• A. 5:6
• B. 6:5 (Correct)
• C. 4:5
• D. 3:4

Explanation: A: 4×12=48, B: 5×8=40. Ratio=48:40=6:5.

8. Three vessels hold 30, 40, and 50 litres of mixtures with 40%, 50%, and 60% acid. Combined acid percentage:

• A. 48.3%
• B. 50.8%
• C. 51.7% (Correct)
• D. 53.3%

Explanation: Acid: 12+20+30=62 litres. Total=120. %=62/120×100≈51.7%.

9. Average of 5 consecutive odd numbers is 25. Largest number:

• A. 27
• B. 29 (Correct)
• C. 31
• D. 33

Explanation: Middle = 25. Consecutive odds: 21,23,25,27,29. Largest = 29.

10. Three numbers in ratio 3:4:5 have LCM 600. Sum of numbers:

• A. 120 (Correct)
• B. 180
• C. 240
• D. 300

Explanation: The numbers are 3k, 4k and 5k. Their LCM is 60k, so 60k = 600 and k = 10. Sum = 30 + 40 + 50 = 120.

11. 5 years ago, the ratio of A's and B's ages was 3:4. Present sum of their ages is 94. Present ages are:

• A. A=40,B=54
• B. A=41,B=53 (Correct)
• C. A=42,B=52
• D. A=44,B=50

Explanation: Five years ago the ages were 36 and 48, which are in the ratio 3:4. Present ages are therefore 41 and 53, and their sum is 94.

12. How many kg of rice at ₹18/kg must be mixed with 36 kg at ₹24/kg to get mix at ₹20/kg?

• A. 60 kg
• B. 66 kg
• C. 72 kg (Correct)
• D. 78 kg

Explanation: By alligation: (24−20):(20−18)=4:2=2:1. Cheaper:Costlier=2:1. x:36=2:1 → x=72.

13. Average of 6 numbers is 25. Fifth number is 30 and sixth is 40. Average of the first four numbers is:

• A. 18
• B. 19
• C. 20 (Correct)
• D. 21

Explanation: Sum of all 6 numbers = 150. The fifth and sixth numbers add to 70, so the first four add to 80. Average = 80/4 = 20.

14. If 2x+3y=0, find x:y.

• A. 3:−2 (Correct)
• B. −3:2
• C. 2:−3
• D. 3:2

Explanation: 2x=−3y → x/y=−3/2 → x:y=−3:2 or 3:−2.

15. A, B, C start business with ₹4000, ₹5000, ₹6000. A leaves after 4 months, B after 8 months. C stays for 12 months. Profit ratio:

• A. 4:10:18
• B. 8:20:36
• C. 16:40:72
• D. 2:5:9 (Correct)

Explanation: A: 4000×4=16000, B: 5000×8=40000, C: 6000×12=72000. Ratio=16:40:72=2:5:9.