, WGU D128 MatheMatics for eleMentary eDUcators | Western
Governors University | acaDeMic year 2026/2027 | objective
assessMent coMprehensive exaMination | 100 verifieD
QUestions anD correct ansWer rationales | | Most recent .
INTRODUCTION
Welcome to the WGU D128 Mathematics for Elementary Educators OA Study Guide. This
comprehensive resource is designed to help you prepare for the Objective Assessment in
Mathematics for Elementary Educators, a foundational course at Western Governors University
for students in teacher education programs.
DOMAIN 1: NUMBER SENSE & OPERATIONS
Question 1
Which of the following is a prime number?
A. 15
B. 21
C. 17
D. 27
correct ansWer: C. 17 ✓
rationale: A prime number has exactly two positive divisors: 1 and itself. 17 has no positive
divisors other than 1 and itself, making it prime. 15 is divisible by 3 and 5; 21 is divisible by 3
and 7; 27 is divisible by 3 and 9.
Question 2
What is the least common multiple (LCM) of 6 and 8?
A. 12
B. 18
C. 24
D. 48
correct ansWer: C. 24 ✓
rationale: The multiples of 6 are 6, 12, 18, 24, 30… and the multiples of 8 are 8, 16, 24, 32…
The smallest common multiple is 24.
, Question 3
Which fraction is equivalent to 3/4?
A. 6/5
B. 9/12
C. 2/3
D. 5/8
correct ansWer: B. 9/12 ✓
rationale: Multiplying numerator and denominator of 3/4 by 3 gives 9/12, which is equivalent.
Equivalent fractions are created by multiplying or dividing both the numerator and denominator
by the same non-zero number.
Question 4
What is 25% of 80?
A. 10
B. 15
C. 20
D. 25
correct ansWer: C. 20 ✓
rationale: 25% × 80 = 0.25 × 80 = 20. Percent means "per hundred," so 25% is 25/100 =
0.25.
Question 5
What is the sum of 2/3 and 1/4?
A. 3/7
B. 8/12
C. 11/12
D. 3/12
correct ansWer: C. 11/12 ✓
rationale: To add fractions, find the least common denominator (12), convert 2/3 to 8/12 and
1/4 to 3/12, then add numerators: 8/12 + 3/12 = 11/12. Distractor A reflects the common student
error of adding numerators and denominators separately (2+1=3, 3+4=7).
Question 6
A student calculates 4.25 × 0.6 and gets 255. What is the student's error, and what is the correct
answer?
Governors University | acaDeMic year 2026/2027 | objective
assessMent coMprehensive exaMination | 100 verifieD
QUestions anD correct ansWer rationales | | Most recent .
INTRODUCTION
Welcome to the WGU D128 Mathematics for Elementary Educators OA Study Guide. This
comprehensive resource is designed to help you prepare for the Objective Assessment in
Mathematics for Elementary Educators, a foundational course at Western Governors University
for students in teacher education programs.
DOMAIN 1: NUMBER SENSE & OPERATIONS
Question 1
Which of the following is a prime number?
A. 15
B. 21
C. 17
D. 27
correct ansWer: C. 17 ✓
rationale: A prime number has exactly two positive divisors: 1 and itself. 17 has no positive
divisors other than 1 and itself, making it prime. 15 is divisible by 3 and 5; 21 is divisible by 3
and 7; 27 is divisible by 3 and 9.
Question 2
What is the least common multiple (LCM) of 6 and 8?
A. 12
B. 18
C. 24
D. 48
correct ansWer: C. 24 ✓
rationale: The multiples of 6 are 6, 12, 18, 24, 30… and the multiples of 8 are 8, 16, 24, 32…
The smallest common multiple is 24.
, Question 3
Which fraction is equivalent to 3/4?
A. 6/5
B. 9/12
C. 2/3
D. 5/8
correct ansWer: B. 9/12 ✓
rationale: Multiplying numerator and denominator of 3/4 by 3 gives 9/12, which is equivalent.
Equivalent fractions are created by multiplying or dividing both the numerator and denominator
by the same non-zero number.
Question 4
What is 25% of 80?
A. 10
B. 15
C. 20
D. 25
correct ansWer: C. 20 ✓
rationale: 25% × 80 = 0.25 × 80 = 20. Percent means "per hundred," so 25% is 25/100 =
0.25.
Question 5
What is the sum of 2/3 and 1/4?
A. 3/7
B. 8/12
C. 11/12
D. 3/12
correct ansWer: C. 11/12 ✓
rationale: To add fractions, find the least common denominator (12), convert 2/3 to 8/12 and
1/4 to 3/12, then add numerators: 8/12 + 3/12 = 11/12. Distractor A reflects the common student
error of adding numerators and denominators separately (2+1=3, 3+4=7).
Question 6
A student calculates 4.25 × 0.6 and gets 255. What is the student's error, and what is the correct
answer?
