# 1983 Mathematics JAMB past Questions And Answers from 41 to 50

1983 mathematics 41 to 50

## 41. In the figure below find PRQ

### A. 66½° B. 62½° C. 125° D. 105° E.65°

Solution:

POQ = 360 – 235 = 125°

PRQ x 2 = POQ = 125

PRQ = 125/2 = 62½°

## 42. Simplify 3√(27a⁹/8)

### A. 9a²/2 B. 9a³/2 C. 2/3a² D. 2/3a² E. 3a³/2

Solution:

3√(27a⁹/8) = 3√[3³(a³)³/2³]

= 3a³/2

## 43. The farm yields of four crops on a piece of land in Ondo are represented on the pie chart above. What is the angle of the sector occupied by Okro in the chart?

### A. 91½° B. 19⅓° C. 33⅓° D. 11° E. 91°

Solution:

Beans = 25.6kg, Okro = 14.5kg, Rice = 45.4kg, Yams = 184.5kg

Total kg of the crops = 25.6 + 14.5 + 45.4 + 184.5 = 270kg

Okro occupied 14.5kg

The angle of the sector = 14.5/270 x 360 = 5220/270

= 19⅓°

## 44. In the figure above, PQR is a straight line. Find the values of x and y

### A. x = 22.5° and y = 33.75° B. x = 15° and y = 52.5° C. x = 22.5° and y = 45.0° D. x = 56.25° and y = 11.5° E. x = 18° and y = 56.5°

Solution:

Since PQR is a straight line, that means;

(3x/2 + 3y) + 45 = 180 (Sum of angles on a straight line)

(5x + y) + y = 180 (Sum of angles on a straight line)

3x/2 + 3y = 180 – 45 = 135

3x + 6y = 270

x + 2y = 90. …………….i

5x + 2y = 180…………….ii

Substitute x = 90 – 2y in equation ii

5(90 – 2y) + 2y = 180

450 – 10y + 2y = 180

-8y = 180 – 450 = -270

y = 270/8 = 33.75°

Substitute y = 33.75 in equation i

x + 2(33.75) = 90

x + 67.5 = 90

x = 90 – 67.5 = 22.5°

## 45. PQR is the diameter of a semicircle RSP with centre at Q and radius of length 3.5cm. If QPT = QRT = 60°. Find the perimeter of the figure (PTRS p = 22/7)

### A. 25cm B. 18ccm C. 36cm D. 29cm E. 255cm

Solution:

Radius = PQ = QR = 3.5cm

PR = PQ x 2 = 7cm

PR = PT = RT = 7cm (Sides of equilateral triangle)

PT + RT = 7 + 7 = 14cm

Perimeter of a circle = 2πr

Perimeter of a semicircle = 2πr/2 = πr

= 22/7 x 3.5 = 11cm

Therefore the perimeter of PTRS = 14cm + 11cm

= 25cm

## 46. In a triangle PQR, QR = √3cm, PR = 3cm, PQ = 2√3cm and PQR = 30°. Find angles P and R

### A. P = 60° and R = 90° B. P = 30° and R = 120° C. P = 90° and R = 60° D. P = 60° and R = 60° E. P = 45° and R = 105°

Solution:

Using cosine rule; R² = P² + Q² – 2PQcosR

Cos R = (P² + Q² – R²)/2PQ

= [(√3)² + 3² – (2√3)²]/(2 x √3 x 3)

= (3 + 9 – 12)/10.39 = 0/10.39

Cos R = 0

P = Cos–¹0 = 90°

P = 180 – (30 + 90) = 60°

## 47. In the above diagram if PS = SR and PQ//SR. What is the size of PQR?

### A. 25° B. 50° C. 55° D. 65° E. 75°

Solution:

Since PS = SR , Triangle PSR is an isosceles triangle which has equal bases

SPR = SRP = (180 – 130)/2

= 50/2 = 25°

SRP = RPQ = 25° (Alternate angles)

Therefore PQR = 180 – (100 + 25)

= 180 – 125 = 55°

## 48. Find the mean of the following 24.57, 25.63, 25.32, 26.01, 25.77

### A. 25.12 B. 25.30 C. 25.26 D. 25.50 E. 25.73

Solution:

Mean = (24.57 + 25.63 + 25.32 + 26.01 + 25.77)/5

= 127.3/5 = 25.46 = 25.50

## 49. In the figure above PT is a tangent to the circle with centre O. If PQT = 30°. Find the value of PTO

### A. 30° B. 15° C. 24° D. 12° E. 60°

Solution:

QPT = x + 90

PQT = 30°

QTP = x + 2x = 3x

(x + 90) + 30 + 3x = 180 (Total angles in a triangle)

4x + 120 = 180

4x = 180 – 120 = 60

x = 60/4 = 15°

Thus, PTO = 2x = 2 x 15 = 30°

## 50. A man drove for 4 hours at a certain speed, he then doubled his speed and drove for another 3 hours. Altogether he covered 600km. At what speed did he drive for the last 3 hours?

### A. 120km/hr B. 60km/hr C. 600/7km/hr D. 50km/hr E. 100km/hr.

Solution:

Let the First speed be “y”, Time = 4 hours

Distance = y x 4 = 4y

Second speed is 2y, Time = 3 hours

Distance = 2y x 3 = 6y

4y + 6y = 600

10y = 600

y = 600/10 = 60km/hr

His speed for the last 3 hours is 2y

= 2 x 60 = 120km/hr