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Find the product xy if, x, 3/2, 6/7, y are in G.P

Mathematics
WAEC 1988

Find the product xy if, x, 3/2, 6/7, y are in G.P

  • A. 24/49
  • B. 4/7
  • C. 9/7
  • D. 7/4
  • E. 21/8
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Correct Answer: Option C
Explanation

In GP, when you are given three consecutive terms, say f, g, h, then

\(f \times h = g^2\)

Given: \(x, \frac{3}{2}, \frac{6}{7}, y\), then

\(\frac{6x}{7} = (\frac{3}{2})^2 \implies \frac{6x}{7} = \frac{9}{4} ... (i)\)

Also, \(\frac{3y}{2} = (\frac{6}{7})^2 \implies \frac{3y}{2} = \frac{36}{49} ... (ii)\)

From \(\frac{6x}{7} = \frac{9}{4} \implies x = \frac{9 \times 7}{6 \times 4}\)

\(x = \frac{21}{8}\)

Also, \(\frac{3y}{2} = \frac{36}{49} \implies y = \frac{2 \times 36}{3 \times 49}\)

= \(\frac{24}{49}\)

\(xy = \frac{21}{8} \times \frac{24}{49} = \frac{9}{7}\)


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NECO June/July 2024 - Get offline past questions & answers - Download objective & theory, all in one app 48789
Join your school's WhatsApp group
Post-UTME Past Questions - Original materials are available here - Download PDF for your school of choice + 1 year SMS alerts
Join your school's WhatsApp group
Post-UTME Past Questions - Original materials are available here - Download PDF for your school of choice + 1 year SMS alerts
NECO June/July 2024 - Get offline past questions & answers - Download objective & theory, all in one app 48789