Alan

You need to be careful with units here.  The first question asks for the answer in miles/hr²; the answer is given in m/s².

The second example finds the difference in speeds given in miles/hr and divides by seconds, so the value given has units of miles/(hr.sec).

Just take the right-hand side of Chris's formula and divide top and bottom by (1+r)ⁿ.  

His equation becomes  M = Pr/(1-1/(1+r)ⁿ) or M = Pr/(1-(1+r)^-n)

Replace his P by your A and his r by your i.  

I'll take your word for it Melody!

See Melody's calculation below.

I'll leave you to decide on the conclusion.

PS:  I don't know what you mean by "Use = .10 ..." in your question.

You need to select the LaTeX Formula button from the ribbon and enter your LaTeX into that (I just copied and pasted it below).  

$$\frac{a}{c} + \frac{bc - ad}{c} \left [ \frac{(cx - a + \alpha)\alpha^{n - 1} - (cx - a + \beta)\beta^{n - 1}}{(cx - a + \alpha)\alpha^{n} - (cx - a + \beta)\beta^{n}} \right ]
where:

\alpha = \frac{a + d + \sqrt{(a - d)^2 + 4bc}}{2}
\beta = \frac{a + d - \sqrt{(a - d)^2 + 4bc}}{2}

\left\{b+1,\sum_{i=a}^b g(i)\right\} \equiv \left( \{i,x\} \rightarrow \{ i+1 ,x+g(i) \}\right)^{b-a+1} \{a,0\}
and the equivalent product:

\left\{b+1,\prod_{i=a}^b g(i)\right\} \equiv \left( \{i,x\} \rightarrow \{ i+1 ,x g(i) \}\right)^{b-a+1} \{a,1\}$$

I'm not clear what your question is though!

Here's another way of looking at it (but also by differentiating lnx):

To sum these, first express each with the same denominator.  This is easy to do once we notice that 34 is twice 17, so the fraction -3/17 can be written as -6/34.  Now the sum becomes 9/34 - 6/34, or (9-6)/34, or 3/34.

I guess I should also note that adding a negative number just means subtracting that number, so 9/34 + (-3/17) is the same as 9/34 - (3/17)

If she deposits 30% of her salary, she must spend 70% of her salary, so 70% of her salary is Rs.9800.  This means her salary must be Rs.9800/0.7 or Rs.14000

A picture helps:

1.  sin(θ) = 20/L  ;  L = 20/  sin(θ);    θ = 40°

$${\mathtt{L}} = {\frac{{\mathtt{20}}}{\underset{\,\,\,\,^{\textcolor[rgb]{0.66,0.66,0.66}{360^\circ}}}{{sin}}{\left({\mathtt{40}}^\circ\right)}}} \Rightarrow {\mathtt{L}} = {\mathtt{31.114\: \!476\: \!537\: \!185\: \!947\: \!2}}$$

L = 31 cm to nearest cm

2. Lcos(θ) + 7.3 = L;  L = 7.3/(1 - cos(θ));

$${\mathtt{L}} = {\frac{{\mathtt{7.3}}}{\left({\mathtt{1}}{\mathtt{\,-\,}}\underset{\,\,\,\,^{\textcolor[rgb]{0.66,0.66,0.66}{360^\circ}}}{{cos}}{\left({\mathtt{40}}^\circ\right)}\right)}} \Rightarrow {\mathtt{L}} = {\mathtt{31.202\: \!507\: \!422\: \!010\: \!490\: \!6}}$$

L = 31 cm to nearest cm.