NECO Mathematics Past Questions & Answers - Page 36

176.

Find the 19th term of the A.P. \(\frac{5}{6}\), \(\frac{8}{6}\), \(\frac{11}{6}\).................

A.

7\(\frac{1}{2}\)

B.

9

C.

9\(\frac{1}{2}\)

D.

9\(\frac{5}{6}\)

E.

10

Correct answer is D

first term (a) = \(\frac{5}{6}\)

common difference =   \(\frac{8}{6}\) - \(\frac{5}{6}\) → \(\frac{3}{6}\) or \(\frac{1}{2}\)

A.P formula → T\(_n\) = a + (n - 1)d
T\(_n\) = \(\frac{5}{6}\) + (19 - 1)\(\frac{1}{2}\)
T\(_n\) = \(\frac{5}{6}\) + 9

→ 9\(\frac{5}{6}\)

177.

Mr Aborowa bought a car for N200,000.00 and later sold it for N170,000.00. What is the percentage loss?

A.

11.60%

B.

7.60%

C.

15%

D.

17.65%

Correct answer is C

Using these:

Loss = C.p - S.p

: Percentage Loss = ( Loss X 100) ÷ C.p

=15 %

178.

If s = \(\sqrt{(\frac{a^2}{x^2} - \frac{b^2}{y^2})}\)what does y equal?

A.

\(\sqrt{\frac{(b^2 - a^2)}{(s^2 - x^2)}}\)

B.

\(\sqrt{\frac{(b^2 - a^2)}{(s^2 \times 2)}}\)

C.

\(\sqrt{\frac{x^2 - a^2 - b^2}{s}}\)

D.

\(\frac{x^2 - a^2 - b^2}{s}\)

E.

\(\sqrt{\frac{(b^2 x^2)}{(a^2 - s^2 x^2)}}\)

Correct answer is E

s = \(\sqrt{(\frac{a^2}{x^2} - \frac{b^2}{y^2})}\)

s\(^2\) = \(\frac{a^2}{x^2} - \frac{b^2}{y^2}\)

\(\frac{b^2}{y^2}\) = \(\frac{a^2}{x^2}\) - s\(^2\)

\(\frac{b^2}{y^2}\) = \(\frac{a^2 - s^2 x^2}{x^2}\)

\(\frac{1}{y^2}\) = \((\frac{a^2 - s^2 x^2}{x^2}) \times \frac{1}{b^2}\)

\(\frac{1}{y^2}\) = \(\frac{a^2 - s^2 x^2}{b^2 x^2}\)

\(\therefore\) y\(^2\) = \(\frac{b^2 x^2}{a^2 - s^2 x^2}\)

y = \(\sqrt{\frac{b^2 x^2}{a^2 - s^2 x^2}}\)