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JAMB Mathematics Past Questions & Answers - Page 96

476.

The area of a circle of radius 4cm is equal to (Take π = 3.142 )

A.

10.3cm2

B.

15.7cm2

C.

50.3cm2

D.

17.4cm2

Correct answer is C

Area of a circle (A) = πr2

Radius = 4cm

π = 3.142

A = 3.142 × (4)2

= 3.142 × 16

= 50.272

A = 50.3cm2 (1dp)

477.

Simplify 1(x+1)+1(x1)

A.

2x/(x + 1)(x−3)

B.

2x/(x + 1)(x−1)

C.

2x/(x + 1)2

D.

2x(x+1)2

Correct answer is B

[1 ÷ (x+1)] + [1 ÷ (x − 1)]

= ((x − 1) + [(x + 1)) ÷ (x+1)(x − 1)]

Using the L.C.M.

= (x − 1 + x + 1) ÷ (x + 1)(x − 1)

= (x + 2 − 1 + 1) ÷ (x + 1)(x − 1)

= 2x ÷ (x + 1)(x − 1) =2x ÷ (x + 1)(x − 1)

478.

Find the area of the curved surface of a cone whose base radius is 3cm and whose height is 4cm (π = 3.14)

A.

17.1cm2

B.

27.2cm2

C.

47.1cm2

D.

37.3cm2

Correct answer is C

Find the slant height

l2=h2+r2(h=4cm,r=3cm)

l2=42+32=16+9=25

l2=25

Squaring both sides

l = 5cm

The area of curved surface (s) =π(3)(5)

15π = 15 × 3.14

= 47.1cm2

479.

Integral ∫(5x3+7x22x+5)dx

A.

5x44+7x33+2x+C

B.

5x44+7x33x2+5x+C

C.

5x33+7x2xx+C

D.

2x23+x5C

Correct answer is B

(5x3+7x22x+5)dx

= 5x44+7x332x22+5x+c

= 5x44+7x33x2+5x+c

480.

Evaluate log5(y2x5÷125b½)

A.

2 log5y + 5log5 y2 − 3

B.

log5 y2 + 5log5 x + 3

C.

25logy 5 + 3

D.

2log5y + 5log5x − ½ log5b −3

Correct answer is D

log5(y2x5÷125b12)

= log5y2+log5x5[log5125+log5b12

= 2log5y+5log5xlog55312log5b

= 2log5y+5log5x312log5b