ECZ 2010 · O-Level Paper 2 · Question 6 — Vectors In Two Dimensions

Question from ECZ 2010 · O-Level Paper 2 · Question 6

(a) The diagram below shows a trapezium in which OA = a, OC = c and CB is parallel to OA. CB is twice OA, the points D and E are midpoints of AB and CB respectively. Express in terms of a and/or c the following vectors

Diagram for part (a)

(a(i)) CA,[1]

Verified working — step 1

Route C to A through O.

(a(ii)) AB,[1]

Verified working — step 1

Route A to B through O and C.

(a(iii)) EB,[2]

Verified working — step 1

E is the midpoint of CB, and CB = 2a.

(a(iv)) OD,[2]

Verified working — step 1

D is the midpoint of AB, so OD = OA + (12)AB.

(a(v)) BO.[1]

Verified working — step 1

OB = OA + AB = a + (a + c) = 2a + c.

(b) At one college, a group of 25 students were asked which Cell Phone service providers they subscribed to. The results are shown in the Venn diagram below.

Diagram for part (b)

(b(i)) Calculate the value of x.[1]

Verified working — step 1

All the Venn regions add to 25.

(b(ii)) Given that G = {Glo}, R = {Rodgers} and D = {Du}, find,

(b(ii)(a)) n(G ∩ R)[1]

Verified working — step 1

n(G intersect R) is the overlap of the Glo and Rodgers circles.

(b(ii)(b)) n(D ∪ G').[2]

Verified working — step 1

G holds 10 + 3 = 13 students, so G' holds 25 - 13 = 12.

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Original examination question © Examinations Council of Zambia. Worked solution and commentary © G12 Titan — not to be reproduced without permission.

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