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WAEC Further Mathematics Past Questions & Answers - Page 40

196.

If nC2 = 15, find the value of n

A.

8

B.

7

C.

6

D.

5

Correct answer is C

nC2 = 15

n!(n3)!2! = 15

n(n1)(n2)!(n2)!2 = 15 

n2 - n = 30

n2 - n - 30 = 0

(n - 6)(n + 5) = 0

n = 6 or n = -5 

197.

Rationalize; 12+1

A.

2 - 1

B.

1 - 2

C.

212

D.

122

Correct answer is A

12+1 x 2121

= 2121

= 211=21

198.

Evaluate tan 75o; leaving the answer in surd form (radicals) 

A.

3+2

B.

3+1

C.

31

D.

32

Correct answer is D

Tan 75o = Tan (45o + 30o)

= tan45o+tan30o1tan45otan30o

3+131

RATIONALIZE THE DENOMINATOR

= 3+1313+13+1

4+2331

2(2+3)2

= 2 + 3

199.

Solve; P2+k3 = 5 and 2p = k = 6 simultaneously

A.

p = -6, k = -6

B.

p = -6, k = 6

C.

p = 6, k = 6

D.

p = 6, k = -6

Correct answer is C

P2+k3 = 5

3p+2k6 = 5

2p + 3k = 30

- 2p - k = 6

¯4k4=244 

k = 6

 

From 2p - k = 6

2p - 6 = 6

2p2=122

p = 6

200.

Solve: 8x2 = 43x

A.

-2

B.

-1

C.

1

D.

2

Correct answer is B

8x2 = 43x

23(x2) = 22(3x)

2 3x4 = 26x

2 x4  = 6x

4x4 = 44

x = -1