# Mathematics 2021 Past Questions | WAEC

Study the following Mathematics past questions and answers for JAMB, WAEC NECO and Post-JAMB. Get prepared with official past questions and answers for upcoming examinations.

- Correct, 0.00798516 to
**three**significant figures

- A. 0109
- B. 0800
- C. 00799
- D. 0.008

**Correct Option: Answer is C**

First 2 non-zero digits from the start, ignore the zeros and count from digit 7

0.00798516

0.00798516 =0.00799 to 3 s.f,

**2. **Simplify (11_{two})^{2}

- A. 1001
_{two} - B. 1101
_{two} - C. 101
_{two} - D. 10001
_{two}

**Correct Option: Answer is B**

11

__11__

11

__ 11__

__1101 _{two}__

**3. **Solve = 2\(^\sqrt{2x+1}\) = 32

- A. 13
- B. 24
- C. 12
- D.11

**Correct Option: Answer is C**

2\(^\sqrt{2x+1}\) = 32 ;

2\(^\sqrt{2x+1}\) = 2\(^5\)

\(\sqrt{2x+1}\) = 5

2x+1 =5^{2}

2x+1=25; 2x =25-1

2x =24; x =12

**4. **If log_{10}^{2} =m and log_{10}^{3} =n, find log_{10}^{24 }In term of m and n.

- A. 3m+n
- B. m+3n
- C. 4mn
- D. 3mn

**Correct Option: Answer is A**

log_{10}^{24 }= log_{10}^{4 x 3x 2}= log_{10}^{4}+ log_{10}^{3}+ log_{10}^{2}

2log_{10}^{2 }+ log_{10}^{3}+ log_{10}^{2}

=2m + n + m

3m+n

**5. **Find the 5^{th} term of the sequence 5, 10, 17, …….

**A.**22**B.**24**C.**36**D.**26

**Correct Option: Answer is D**

**6. **If P = {-3<x<1} and Q ={-1<x<3}, where x is a real number find, P n Q.

**A.**{-1<x<1}**B.**{-3<x<1}**C.**{-1<x<1}**D.**{-1<x<1}

**Correct Option: Answer is D**

**7. **Factorize 6pq-3rs-3ps + 6qr

**A.**(3r-p) (2q + s)**B.**3(p + r)(2q-s)**C.**3(p – r)(2q-s)**D.**(3r-p)(s-2q)

**Correct Option: Answer is B**

6pq – 3rs – 3ps +6qr

=3(2pq – rs – 3ps +2qr)

=(2pq – rs – 3ps +2qr)=(2pq-ps)+(2qr-rs)

=(2pq-ps)+(2qr-rs)

Factor out p in the first and r in the second

p(2q-s)+r(2q-s); (2q-s)(p+r)= 3(p + r)(2q-s)

**8. **What number should be subtracted from the sum of 2 1/6 and 2 7/12 to give 3 ¼.

**A.**1/3**B.**1 1/2**C.**1 1/6**D.**1/2

**Correct Option: Answer is B**

x = 2 1/6 + 2 7/12 = 13/6 + 31/12 =13/4

57/12 = 19/4 – 13/4 = 6/4 = 1 1/2

**9. **Mensah is 5 years old and Joyce is **thrice **as old as Mensah. In how many years will Joyce be **twice **as old as Mensah?

**A.**3 years**B.**10 years**C.**5 years**D.**15 years

**Correct Option: Answer is C**

Let J = Joyce’s age

and M = Mensah’s age

(1) J = 3*M = 3*5 = 15 (for current ages)

(2) 2(5 + x) = 15 + x (for future ages, unknown is “x” years for condition 2xM = J to be met)

Multiply left side both by 2:

10 + 2x = 15 + x

Subtract x from both sides:

10 + x = 15

Subtract 10 from both sides:

x = 5

**10. **If 16 x 2^{(x+1)} = 4^{x} x 8^{(1-x)}, find the value of x.

**A. -4****B. 4****C.**1**D.**-1

**Correct Option: Answer is C**

= 16 x 2^{(x+1)} = 4^{x} x 8^{(1-x)}

=32^{(x+1)} =32^{x(1-x)} ; x+1= x-x^{2}

x-x^{2 }-x-1=0; x^{2} -1= 0; x=1

**11. **The circumference of a circular track is 9 km. A cyclist rides round it a number of times and stops after covering a distance of 302km. How far is the cyclist from the starting point?

**A.**5km**B.**6km**C.**7km**D.**3km

**Correct Option: Answer is A**

**Correct Option: Answer is A**

**12. **Simplify 2\(\sqrt{7}\) – \(\frac{14}{\sqrt{7}}\) + \(\frac{7}{\sqrt{21}}\)

**A.**\(\frac{\sqrt{21}}{21}\)**B.**7\(\frac{\sqrt{21}}{3}\)**C.**\(\frac{\sqrt{21}}{3}\)**D.**2\(\sqrt{3}\)

**Correct Option: Answer is A**

**13. **If 4x +2y =16 and 6x – 2y = 4, find the value of (y-x)

**A.**8**B.**2**C.**4**D.**6

**Correct Option: Answer is B**

4x +2y =16 x 6

6x – 2y = 4 x 4

24x + 12y = 96

__24x – 8y = 16__

20y = 80

Y=4

Substitute for y in eqn 1

4x + 2(4) =16; 4x +8 =16

4x =16 -8; 4x=8; x=2

Therefore, y-x=4-2=2

**14. **Given that R is directly proportional to L and inversely proportional to P, R=3 when L =9 and P=0.8, find R when L=15 and P =1.8

**A.**2.2**B.**3.3**C.**6.6**D.**0.3

**Correct Option: Answer is A**

**15.**In the diagram, angle ABC and angle BCD are right angles, angle BAD = t and and angle EDF = 70

^{o}, find the value of t.

**A.**70\(^o\)**B.**165\(^o\)**C.**140\(^o\)**D.**110\(^o\)