Mathematics questions and answers

Mathematics Questions and Answers

How good are you with figures and formulas? Find out with these Mathematics past questions and answers. This Test is useful for both job aptitude test candidates and students preparing for JAMB, WAEC, NECO or Post UTME.

3,781.

If the 7th term of an AP is twice the third term and the sum of the first four terms is 42, find the common difference.

A.

6

B.

3

C.

2

D.

1

Correct answer is B

U7 = a + (7 - 1)d
= a + 6d
U3 = a + (3 - 1)d
= a + 2d
But U7 = 2(U3)
∴a + 6d = 2(a + 2d)
a + 6d = 2a + 4d
2a - a + 4d - 6d = 0
a - 2d = 0 → eqn1
Sn = n/2 (2a + (n - 1)d)
42 = 4/2 (2a + (4 - 1)d)
42 = 2(2a + 3d)
21 = 2a + 3d → eqn2
eqn1 * eqn2 0 = 2a - 4d
21 = 7d
∴d = 21/7
d = 3

3,782.

Find the range of values of x for which 7x - 3 > 25 + 3x

A.

x >7

B.

x<7

C.

x>-7

D.

x<-7

Correct answer is A

7x - 3 > 25 + 3x
7x - 3x > 25 + 3
4x > 28
x > 28/4
x > 7

3,783.

The weight W kg of a metal bar varies jointly as its length L meters and the square of its diameter d meters. If w = 140 when d = 42/3 and L = 54, find d in terms of W and L.

A.

\(\sqrt{\frac{42W}{5L}}\)

B.

\(\sqrt{\frac{6L}{42W}}\)

C.

\(\frac{42W}{5L}\)

D.

\(\frac{5L}{42W}\)

Correct answer is A

\(W\infty LD^2\\W=KLd^2\\K=\frac{W}{Ld^2}\\=\frac{140}{54}\times\left(4\frac{2}{3}\right)^2 \\=\frac{140}{54}\times\left(\frac{14}{3}\right)^2\\=\frac{140\times 9}{54\times 14\times 14}\\=\frac{5}{42}\\∴W=\frac{5}{42Ld^2}\\42W=5Ld^2\\\frac{42W}{5L}=d^2\\d=\sqrt{\frac{42W}{5L}}\)

3,784.

The time taken to do a piece of work is inversely proportional to the number of men employed. If it takes 30 men to do a piece of work in 6 days, how many men are required to do the work in 4 days?

A.

20

B.

35

C.

45

D.

60

Correct answer is C

t = time taken and N = number of men
t ∝ 1/N
t = K/N
K = Nt
K = 30 * 6
K = 180
∴t = 180/N
4 = 180/N
4N = 180
N = 180/4
45 men

3,785.

A polynomial in x whose zeros are -2, -1 and 3 is

A.

x3 - 7x + 6

B.

x3 + 7x - 6

C.

x3 + 7x + 6

D.

x3 - 7x - 6

Correct answer is D

x = -2, x = -1 and x = 3
∴x+2 = 0, x+1 = 0 and x-3 = 0
Product of the factors
(x+2)(x+1)(x-3) = 0
(x2 + 3x + 2)(x-3)
x(x2 + 3x + 2) -3(x2 + 3x + 2) = 0
x3 + 3x2 + 2x - 3x2 - 9x - 6 = 0
x3 - 7x - 6 = 0