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3 questions · timed · auto-graded

Question 15 Marks
Evaluate: $\left[\left(\frac{5}{6}\right)^2 \times \frac{9}{4}\right] \div\left[\left(-\frac{3^2}{2}\right) \times \frac{125}{216}\right]$
Answer

$\begin{aligned} & {\left[\left(\frac{5}{6}\right)^2 \times \frac{9}{4}\right] \div\left[\left(-\frac{3^2}{2}\right) \times \frac{125}{216}\right]} \\ & =\left[\frac{5 \times 5}{6 \times 6} \times \frac{9}{4}\right] \div\left[\frac{-3 \times-3}{2 \times 2} \times \frac{125}{216}\right] \\ & =\left[\frac{25}{36} \times \frac{9}{4}\right] \div\left[\frac{9}{4} \times \frac{125}{216}\right] \\ & =\left[\frac{25}{4} \times \frac{1}{4}\right] \div\left[\frac{1}{4} \times \frac{125}{24}\right] \\ & =\left[\frac{25}{16}\right] \div\left[\frac{125}{96}\right] \\ & =\frac{25}{16} \times \frac{96}{125} \\ & =\frac{1}{1} \times \frac{6}{5}=1 \frac{1}{5}\end{aligned}$
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Question 25 Marks
Simplify and express the Solution in the positive exponent form:
$-\frac{128}{2187}$
Answer

$-\frac{128}{2187}$
2128
264
232
216
28
24
22
1
32187
3729
3243
381
327
39
33
1

$-\frac{2 \times 2 \times 2 \times 2 \times 2 \times 2 \times 2}{3 \times 3 \times 3 \times 3 \times 3 \times 3 \times 3}=-\frac{2^7}{3^7}$
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Question 35 Marks
If $64 x 625 = 2^a x 5^b $; find: the values of a and b.
Answer
the values of a and b.
$64 x 625 = 2^a x 5^b$
$64 = 2^a$
$2$ $64$
$2$ $32$
$2$ $16$
$2$ $8$
$2$ $4$
$2$ $2$
  $1$
$64 = 2 \times 2 \times 2 \times 2 \times 2 \times 2$
$64 = 2^6$
$\therefore a = 6$
Also, $625 = 5^b​​​​​​​$​​​​​​​
$5$ $625$
$5$ $125$
$5$ $25$
$5$ $5$
  $1$
$625 = 5 \times 5 \times 5 \times 5$
$625 = 5^4$
$\therefore b = 4$
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[5 marks sum] - MATHS STD 7 Questions - Vidyadip