GMAT Quantitative Quiz: Calculate Central Tendency

What this quiz covers

This quiz focuses on Calculate Central Tendency, giving you a quick way to practice the rules, question types, and explanations that matter most for GMAT Quantitative.

How to use this quiz

Try each quiz question before looking at the correct answer. Use the explanations to review missed ideas, then come back to similar questions until the pattern feels familiar.

Question 1

1. 48.0 (correct answer)
2. 48.5
3. 49.0
4. 49.5

Explanation: Original mean = 50, so total sum = 20 × 50 = 1000. When the 5 largest values are each decreased by 8, the total decrease in sum = 5 × 8 = 40. New sum = 1000 - 40 = 960. New mean = 960 ÷ 20 = 48.0. The median information is given as a distractor - it doesn't affect the calculation of the new mean when we know the original mean and the specific changes made.

Question 2

1. 84
2. 86
3. 87 (correct answer)
4. 90

Explanation: Let T = Teamwork score. Weighted average formula: 0.40(85) + 0.35(92) + 0.25(T) = 88. Calculate: 0.40(85) = 34, 0.35(92) = 32.2. So: 34 + 32.2 + 0.25T = 88, which gives 66.2 + 0.25T = 88. Therefore: 0.25T = 88 - 66.2 = 21.8, so T = 21.8 ÷ 0.25 = 87.2 ≈ 87.

Question 3

1. 4
2. 5 (correct answer)
3. 6
4. 7

Explanation: The bar heights are 3, 7, 4, 6, 2, 9, and 5. Ordered from least to greatest: 2, 3, 4, 5, 6, 7, 9. The middle (4th) value is 5, so the median is 5. A) 4 and C) 6 are the two values adjacent to the median but not the middle; D) 7 is larger than the median because it sits farther to the right in the ordered list.

Question 4

1. 28.7
2. 29.9 (correct answer)
3. 30.6
4. 31.5

Explanation: Midpoints: 22,27,32,37. Weighted sum $6(22)+12(27)+15(32)+7(37)=1195$; $1195/40=29.875\approx29.9$. A) 28.7 uses wrong midpoint for 30–34; C) 30.6 mis-weights 35–39; D) 31.5 assumes each bin midpoint is 1 unit higher.

Question 5

1. 8
2. 9
3. 10 (correct answer)
4. 11

Explanation: The highest value on the graph is $78^{\circ}F$ and the lowest is $68^{\circ}F$. Range $=78-68=10$. A) 8 and B) 9 result from mis-reading the extremes; D) 11 comes from subtracting 67 from 78, using an incorrect low point.

Question 6

1. 76.4
2. 77.2
3. 78 (correct answer)
4. 78.8

Explanation: Scores (each dot represents one student): 70,72,74,74,75,76,78,78,80,82,84. Sum $=858$; eleven scores ⇒ $858/11=78$. A) 76.4 omits 84; B) 77.2 mis-counts 74 twice; D) 78.8 double-counts 82.

Question 7

1. 1.2
2. 1.8 (correct answer)
3. 2.4
4. 3

Explanation: Weighted average: $0.60(5)+0.40(-3)=3-1.2=1.8\%$. A) 1.2 uses the negative branch only; C) 2.4 multiplies 0.60 by 4; D) 3.0 ignores the loss branch.

Question 8

1. 12
2. 16 (correct answer)
3. 18
4. 20

Explanation: Counts: Marketing 20, Finance 16, HR 12, Operations 24, IT 8. Ordered: 8,12,16,20,24 ⇒ median is 16. A) 12 and D) 20 are adjacent values, not the middle; C) 18 is an average of 16 and 20, not an actual count.