WAEC Mathematics Past Questions & Answers - Page 127

y = mx + c; when x = 0; y = 1

1 = m(0) + c; 1 = 0 + c; c = 1

when x = 2; y = 2

2 = m(2) + c; 2 = 2m + c; but c = 1

2 = 2m + 1

2 - 1 = 2m

2m = 1

m = $\frac{1}{2}$

y = $\frac{1}{2}$x + 1

mean age = $\frac{\text{sum of ages}}{\text{no. of men}}$

50 = \9\frac{sum}{R}\)

sum = 50R.....(1)

Sum of ages of the men that left = 55 + 63 = 188

remaining sum = 50R - 118

remaining no. of men = R - 2

now mean age = 50 - 1 = 49 years

49 = $\frac{50R - 118}{R - 2}$

49(R - 2) = 50R - 118

49R - 50R = -188 - 98

-R = -20

R = 20

s.p = N6900

%profit = 15%

%profit = $\frac{s.p - c.p}{c.p}$ x 100%

15% = $\frac{6900 - c.p}{c.p}$ x 100%

$\frac{15}{100}$c.p = N6900 - c.p

0.15 c.p = N6900 - c.p

1.15c.p + c.p = N6900

c.p = $\frac{6900}{1.15}$

= 6000.00

Now new S.P = N6600

profit = s.p - c.p = 6000 - 6600

= 600

%profit = $\frac{600}{6600}$ x 100%

= 10%

No. of times = $\frac{\text{Total distance}}{\text{Circumference of circle}}$

= $\frac{\text{Total distance}}{\pi d}$

= $\frac{1000m}{\frac{22}{7} \times 100m}$

= $\frac{1000 \times 7}{2200} = 3.187$

= 3(approx.) nearest whole no.

sequence: -2, 4, -8, 16........{GP}

a = -2; r = $\frac{4}{-2}$ = -2

nth term T_n = ar^n-1

T_n = (-2)(-2)^^n-1

T_n = (-2)^{1 + n - 1}

T_n = (-2)ⁿ