Alan

PEMDAS:   Parentheses; Exponents; Multiplication; Division; Addition; Subtraction

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v = √(G*M/r) can be rewritten as v² = G*M/r, which can then be rearranged as r = G*M/v²

$${\mathtt{r}} = {\frac{{\mathtt{6.67}}{\mathtt{\,\times\,}}{{\mathtt{10}}}^{\left(-{\mathtt{11}}\right)}{\mathtt{\,\times\,}}{\mathtt{2}}{\mathtt{\,\times\,}}{{\mathtt{10}}}^{\left({\mathtt{30}}\right)}}{{\left({\mathtt{2}}{\mathtt{\,\times\,}}{{\mathtt{10}}}^{{\mathtt{4}}}\right)}^{{\mathtt{2}}}}} \Rightarrow {\mathtt{r}} = {\mathtt{333\,500\,000\,000}}$$

r = 3.335*10¹¹ m

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If all products are the same price p, you are paying 0.8*12p, but at full price for all 13 you would pay 13p.

So the discount is (1 - 0.8*12p/13p)*100% ≈ 26.15%

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(-2)^2 = 4  but -2^2 = -4 because exponentiation (raising to a power) takes a higher priority than negation.  Any good scientific calculator should do this.

6/2 = 3 and 21/7 = 3, so the factor is 3

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10*(n/2 + 6) = 8

10*n/2  +  10*6 = 8

5*n   +  60 = 8

Subtract 60 from both sides

5*n = -52

Divide both sides by 5

n = - 10.4

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1 mile = 1.609344 km

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$$5.33333.....=5\frac{1}{3}$$

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There are 3600 seconds in an hour so divide 3600 by 11

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0.09 is ten times as big as 0.009

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