Simplify \(\frac{5+\sqrt{7}}{3+\sqrt{7}}\)
17-√7
4-√7
15+√7
7-√7
Correct answer is B
\(\frac{5+\sqrt{7}}{3+\sqrt{7}}=\frac{5+\sqrt{7}}{3+\sqrt{7}}\times \frac{3-\sqrt{7}}{3-\sqrt{7}}\\
=\frac{(5+\sqrt{7})(3-\sqrt{7})}{3^2 - \sqrt{7}^2}\\
=\frac{15-5\sqrt{7}+3\sqrt{7}-7}{9-7}\\
=\frac{8-2\sqrt{7}}{2}\)
Factorize then divide by 2
\(=\frac{2(4-\sqrt{7}}{2}\\
=4-\sqrt{7}\)
If log\(_{10}\)2 = 0.3010 and log\(_{10}\)7 = 0.8451, evaluate log\(_{10}\)280
3.4471
2.4471
1.4471
1.4071
Correct answer is B
Log 2 = 0.3010, Log 7 = 0.8451
∴Log 280 = Log 28 x 10
= Log 7x4x10
=Log7 + Log4 + Log10
= Log7 + Log2\(^2\) + Log10
= Log7 + 2Log2 + Log10
= 0.8451 + 2(0.3010) + 1
= 0.8451 + 0.6020 + 1
= 2.4471
7/15
8/15
2/5
4/5
Correct answer is C
Let his allowance = y.
\(Books = \frac{y}{5}\)
\(Remainder: y - \frac{y}{5} = \frac{4y}{5}\)
\(Food: \frac{1}{2} \times \frac{4y}{5} = \frac{2y}{5}\)
\(Contingencies: \frac{4y}{5} - \frac{2y}{5} = \frac{2y}{5}\)
Therefore, he kept \(\frac{2}{5}\) of his allowance for contingencies.
N37,550
N40,400
N41,400
N42,400
Correct answer is C
C.P = N34000 + N2000 = N36000
Gain = 100 + 15 = 115%
S.P = \(\frac{115}{100}\times \frac{N3600}{1}\)
= N41400
Evaluate \(\frac{81.81+99.44}{20.09+36.16}\) correct to 3 significant figures.
6.24
3.22
2.78
2.13
Correct answer is B
\(\frac{81.81 + 99.44}{20.09 + 36.16}\\
=\frac{181.25}{56.25}\\
=\frac{18125}{5625}\\
\frac{29}{9}\\
=3\frac{2}{9}\\
≅ 3.22\)