JAMB Mathematics Past Questions & Answers - Page 233

1,161.

If x is the addition of the prime numbers between 1 and 6; and y the H.C.F. of 6, 9, 15. Find the product of x and y

A.

27

B.

30

C.

33

D.

90

Correct answer is B

Prime numbers between 1 and 6 are 2, 3 and 5 x = 2 + 3 = 5 = 10 H.C.F. of 6, 9, 15 = 3 ∴ y = 3 X x y = 10 x 3 = 30

1,163.
1,164.

Find correct to one decimal place, 0.24633 \(\div\) 0.0306

A.

0.8

B.

1.8

C.

8.0

D.

8.1

Correct answer is D

\(\frac{0.24633}{0.03060}\) multiplying throughout by 100,000

= \(\frac{24633}{3060}\)

= 8.05

= 8.1

1,165.

If 7 and 189 are the first and fourth terms of geometric progression respectively, find the sum of the first three terms of the progression

A.

182

B.

91

C.

63

D.

28

Correct answer is B

\(T_{n} = ar^{n - 1}\) (nth term of a G.P)

\(T_{4} = ar^{3} = 189\)

\(7 \times r^{3} = 189 \implies r^{3} = 27\)

\(r = \sqrt[3]{27} = 3\)

\(S_{n} = \frac{a(r^{n} - 1)}{r - 1}\)

\(S_{3} = \frac{7(3^{3} - 1)}{3 - 1} \)

= \(\frac{7 \times 26}{2} = 91\)