geno3141

The formula for the surface area of a sphere is:  SA  =  4·π·r²

The formula for the volume of a sphere is:          V   =  4/3·π·r³

Use the surface area to find the radius:     

           SA  =  4·π·r²

           90790  = 4·π·r²     --->     r²  ≈  7224.8386     --->     r   ≈  85 cm

Now, put that value into the formula for the volume of a sphere:

         V  =  4/3 ·π·(85)³

and finish ...

Math can be hard, very hard; but so can everything else is this world.

Math may become easier to you if you try to figure out, in your own words, why the rules are true. If you only memorize rules, without figuring why they work, math can be very confusing and very difficult.

Without figuring things out so they make sense to you, math may seem like it's a million rules that don't make any sense.

If you try to understand what's going on, you find that there are not so many rules, they are just used over and over, in a variety of situations and a variety of ways.

For instance, the rules for exponents:

If you multiply two numbers with the same base, you add the exponents but if you have a power to a power then you multiply the exponents. True, this sounds like gobblegook, but look at it this way:

What is  x² · x³  ?  The first rule says that you have to add exponents, but why?

    x²  =  x · x              x³  =  x · x · x         So: x² ·  x³  = x · x ·  x · x · x  =  x^5

   If you have a box of 2 x's and you combine it with a box of 3 x's, don't you have a box with 5 x's?

   Since you're dumping 2 things with 3 things, you have 5 things; that's adding.

Now, what is  (x²)³ ?  Well, inside each box you have 2 x's and that little exponent of 3 means that you have 3 boxes, so to figure out how many things are in 3 boxes of 2 things each, don't you multiply? And that's why you get 6.

Hang in there; ask when you need help; and try to turn the rules into things that make sense to you.

'Expand' usually means that you need to use the distributive property (or an extended distributive property); for example:  Expand:     6x(2x² - 4x + 7)             [Answer is 12x^3 -24x² + 42x]

'Evaluate' usually means to enter values for variables and simplify to get the answer;                                      for example:  Evaluate when  x = 2  and  y = 5:     3xy + x - y        [Answer is 27] 

Since the pressure increases at the rate of 64 pounds/sq ft for each foot of descent,

the amount of increase can be written as  64 · n  where  n  represents the number of feet of descent. 

Initial Pressure + Increased Pressure Due To Depth  =  Final Pressure

    2120 lb/ft²   +          (64 lb/ft²/ft) · (n ft)             =      7240 lb/ft²

                                                   (64 lb/ft²) · n ft   =   5120 lb/ft²

                                                                        n   =   80 ft

First way: find the number of books on the shelves and the number of books on the tables and add those two                    answers together:   (7 shelves) x (12 books per shelf)  +  (4 tables)x (12 books per table)

                       =   7 x 12  +  4 x 12          =         84  +  48         =         132 books

Second way: since each shelf and each table holds the same number of books, add the number of shelves to                         the number of shelves to the number of tables and then multiply that answer by 12:

                     (7 shelves + 4 tables) x (12 books per location)          11  x  12          =          132 books 

Find invcos(0.6283)

or (2nd) cos(0.6283)

Your answer should be slightly larger than 51°.

The same as if Sally has a Ferrari and Jimmy has a doughnut.

8^n  =  2^k

Get the same base, turn  8  =  2³

Now, you can replace  8  with  2³  into the original formula:   ( 2³ ) ^ n  =  2 ^ k

If you have an exponent to an exponent, mutiply the exponents:  so,  ( 2³ ) ^ n  =  2 ^ (3n)

     2 ^ (3n)  =  2 ^ k             This will only be true if  3n  =  k

Since you want  n  over  k,  divide both sides by  k:  3n / k  =  k / k     --->  3n / k  =  1

Now, finish this by dividing both sides by 3     --->   n / k  =  1 / 3

multiply before you subtract, so multiply 2 x =2  =  -4

Then subtract:   -4 - 2  =  -6

We'll have to calculate how much will be paid over the course of those 17 years.

To do that, we'll first have to calculate how much each monthly payment is.