Some problems that ave been giving me trouble

**Xplicit** · November 29th 2007, 08:28 AM

16-X
------ = 2+x (thats a fraction lol)

5

Find the equation of the line joining the points (0,5) and (2,11)

Calculate

4 and 1 fifth (multiplied by) 1 and 1 seventh

(not sure how to type that out)

Nuno borrowed £400 for 9 months and paid £36 interest. What was the equivalent rate of interest per annum?

Also if you could show me how you got the answer it would help greatly.

thanks in advance for any help

**topsquark** · November 29th 2007, 08:56 AM

Originally Posted by Xplicit

16-X
------ = 2+x (thats a fraction lol)

5

Just so you know, there is a difference between the variables X and x.

$\frac{16 - x}{5} = 2 + x$

$\frac{16 - x}{5} \cdot 5 = (2 + x) \cdot 5$

$16 - x = 10 + 5x$

Can you solve this now?

Originally Posted by Xplicit

Find the equation of the line joining the points (0,5) and (2,11)

Given two points $(x_1, y_1)$ and $(x_2, y_2)$ , the slope of the line going through them may be calculated as
$m = \frac{y_2 - y_1}{x_2 - x_1}$

To get the rest of the equation for the line you can use the slope-intercept form:
$y = mx + b$

Plug in either point and the slope you just calculated and solve for b.

Originally Posted by Xplicit

Calculate
4 and 1 fifth (multiplied by) 1 and 1 seventh

$\left ( 4~\frac{1}{5} \right ) \cdot \left ( 1~\frac{1}{7} \right )$

I am personally against numbers written in this form, though I fully understand why they are useful. But I find that they rather confuse things by the time a student reaches their first Algebra course.

Anyway, I would convert these numbers to improper fractions:
$\left ( 4~\frac{1}{5} \right ) \cdot \left ( 1~\frac{1}{7} \right ) = \frac{21}{5} \cdot \frac{8}{7}$

You should be able to finish this now.

Someone else is going to have to help you with the last problem.

-Dan

**janvdl** · November 29th 2007, 09:06 AM

Originally Posted by Xplicit

Nuno borrowed £400 for 9 months and paid £36 interest. What was the equivalent rate of interest per annum?

This is the formula for simple interest.

$Interest = Capital \ \times \ \frac{Rate}{100} \ \times \frac{Time (Months)}{12 \ Months}$

Thus:

$36 = 400 \times \frac{r}{100} \times \frac{t}{12}$

$36 = 400 \times \frac{r}{100} \times \frac{9}{12}$

$36 = 400 \times \frac{r}{100} \times \frac{3}{4}$

$36 = 300 \times \frac{r}{100}$

$36 = 3r$

$r = 12$

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