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3 years ago

How many 7 digit phone numbers are there assuming the first digit can't be a 0 or a 1?

1 answer:

7 0

The first digit can be any one of the numbers 2-9 That a total of 8 numbers.

The next 6 digits can be any permutation of 6 from the numbers 0 to 9.
(10 numbers)

nPr = n! / r!

so here we have 10P6 = 10! / 6! = 10*9*8*7 = 5040

So final answer is 8 * 5040 = 40,320

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Find two positive real numbers with the given sum whose product is a maximum. The sum of the first and twice the second is 24

Elenna [48]

Y+2x=24
product is max
xy=max

we have
y+2x=24
minus 2x both sides
y=24-2x
sub that for y in xy=max
(24-2x)(x)=max
-2x^2+24x=max
we have a parabola opening down
the coordinates of the vertex is our answer

the x value of the vertex is -b/2a where
ax^2+bx+c=y

-24/2(-2)=-24/-4=6
xvalue=6

we can just sub
y=24-2x
y=24-2(6)
y=24-12
y=12
the numbers are 6 and 12
the product is 72

the numbers are 6 and 12

5 0

4 years ago

PLSSS HELP IF YOU TURLY KNOW THISS

Eduardwww [97]

Answer:

Step-by-step explanation:

3² * 5³ = 3*3 * 5*5*5

= 9 * 125

= 1125

8 0

3 years ago

Read 2 more answers

Bobby Joe and Billy ray went fishing at the local watering hole and caught a total of 51 fish. Billy Rat caught 17 fewer fish th

blondinia [14]

Answer:

Bobby Joe caught 34 fishes

Billy Ray caught 17 fishes

Step-by-step explanation:

Let the number of fish Bobby Joe caught = y

Let the number of Billy Ray caught = x

Total number of fish caught = 51 fishes

x + y = 51......... Equation 1

Billy Ray caught 17 fewer fish than Bobby Joe.

y = x - 17

Write an expression you can use to find out how many fish, f, each boy caught.

Substitute x - 17 for y in Equation 1

x + y = 51......... Equation 1

x + (x - 17) = 51

x + x - 17 = 51

2x = 51 - 17

2x = 34

x = 34/2

x = 17

Hence, Bobby Joe caught 17 fishes

x + y = 51

17 + y = 51

y = 51 - 17

y = 34

Hence, Billy ray caught 34 fishes

5 0

3 years ago

The equation h = 10d represents the height h (in millimeters) that a plant grows after d days. How tall is the plant after 5 day

Elena-2011 [213]

Answer:

50 millimeters

Step-by-step explanation:

d alone , is always 1. Just like any other variable. To find the hegiht you need to do days x 10.

After 5 days its mental math.

just do 5 x 10 and do not forget to add millimeters to the end!

8 0

3 years ago

What is the exact volume of a cylinder that has a radius of 9.2 in. and a height of 3.7 in.?

charle [14.2K]

$The\ volume\ of\ a\ cylinder:V=\pi r^2\cdot H\\/r-a\ radius;\ H-a\ height/\\--------------------\\r=9.2\ in;\ H=3.7\ in\\\\subtitute\\\\V=\pi\cdot9.2^2\cdot3.7=84.64\cdot3.4\pi=\boxed{287.776\pi\ (in^3)}\approx\boxed{903.62\ (in^3)}\\\\Used\ \pi\approx3.14$
and
If the number you are rounding is followed by 5, 6, 7, 8, or 9, round the number up (+1).

If the number you are rounding is followed by 0, 1, 2, 3, or 4, round the number down (no change).

6 0

4 years ago