Tag: maths

The rule of thumb in multiplying decimal numbers is we'll count the decimals from the right-hand side and the total places in the decimal in the question will be in the answer.

$14.79\times 1000 = 14790$

$0.126\times100$

$0.777=7\times 0.111$
$=7\times \frac {1}{9}=\frac {7}{9}$

$4\times 162=648$. Sum of decimal places $= 6$.
So, $0.04\times 0.0162=0.000648=6.48\times { 10 }^{ -4 }$

It can be solved as $27\times 1.\overline {2} \times 5.526\overline {2} \times 0.\overline {6}$
$= 27\times \left (1 + \dfrac {2}{9}\right )\times \dfrac {6}{9} \times (5.526\overline {2})$
$= 27\times \dfrac {11}{9}\times \dfrac {2}{3}\times (5.526\overline {2})$
$= 22\times (5.526\overline {2})$
$= 22\times (5.5 + 0.026\overline {2})$
$= 121 + (22\times 0.026\overline {2})$
$= 121 + 0.\overline {57}$
$= 121.\overline {57}$

$\dfrac { 489.1375\times 0.0483\times 1.956 }{ 0.0873\times 92.581\times 99.749 } \approx \dfrac { 489\times 0.05\times 2 }{ 0.09\times 93\times 100 } $
$=\dfrac { 489 }{ 9\times 93\times 10 } $
$=\dfrac { 163 }{ 279 } \times \dfrac { 1 }{ 10 } $
$=\dfrac { 0.58 }{ 10 } $
$=0.058\approx 0.06$.