Use the unit given.find the volume

A prime number less than 100 is selected randomly. what is the probability that its square has units digit $7$?

liberstina [14]

Any number ends with 0, 1, 2, 3, 4, 5, 6, 7, 8 or 9

Given any number. The square of this number is the last digit of square of the original numbers units digit.

For example

23*23 ends with 9 (3*3=9)

149*149 ends with 1 (9*9=81)

2564*2564 ends with 6 (4*4=16)

and so on

so all the possible unit digits of a square number are {0, 1, 4, 5, 6, 9}

because:

0*0= 0 ; 1*1=1; 2*2=4; 3*3=9; 4*4=16; 5*5=25, 6*6=36; 7*7=49; 8*8=64, 9*9=81

Thus, the probability that the square of a number selected from any set of numbers being 7, is 0.

Answer: 0

4 0

3 years ago

In a theater there are 15 chairs in the first row, each row has 3 more chairs than the previous

andrew11 [14]

Answer:663

Step-by-step explanation:

The first row is 15,so you have to add three from the first row you and you get 18 and then you keep going and going till you get to the 17th row then you add the numbers together.

5 0

3 years ago

Twin brothers, Billy and Bobby, can mow their grandparent’s lawn together in 63 minutes. Billy could mow the lawn by himself in

Pepsi [2]

Answer:

<h2>140 minutes</h2>

Step-by-step explanation:

this problem focuses on the combined work rate

both can finish the work under 63 minute

let bobby mow the lawn in x minute

Billy will then mow the lawn in x-25 minutes

Let the completed job = 1 (a mowed lawn)

we can now apply the combined work formula for the two boys as

$\frac{63}{x}+\frac{63}{x-25}=1$

multiplying through by x(x-25 )we have

$63(x-25)+63x= x(x-25)$

open bracket we have

$63x-1575+63x= x^2-25x$

rearranging and collecting like terms we have

$0=x^2-25x-63x-63x+1575 \\\\0=x^2-151x+1575 \\\\x^2-151x+1575=0$

we can now use the quadractic formula

$x=\frac{-b\frac{+}{} \sqrt{b^2-4ac} }{2a}$

a= 1

b= -151

c= 1575

$x=\frac{-(-151)\frac{+}{} \sqrt{151^2-4*1*1575} }{2*1}$

$x=\frac{-(-151)\frac{+}{} \sqrt{22801-6300} }{2} \\\\x=\frac{-(-151)\frac{+}{} \sqrt{16501} }{2} \\\\x=\frac{-(-151)\frac{+}{} 128.45}{2} \\\\$

$x=\frac{-(-151)+128.45}{2} \\\\\x=\frac{279.45}{2} \\\\x=139.72 \\\\\\x=\frac{-(-151)-128.45}{2}\\\\x=\frac{151-128.45}{2}\\\\x=\frac{22.55}{2}\\\\x=11.27$

the first answer x= 139.72 approximately 140 minutes mins is correct for Bobby's time

let us check

$\frac{63}{140}+\frac{63}{140-25}=1\\\\\\0.45+\frac{63}{115} =1\\\\0.45+0.5478=1\\0.997 =1$

we can see that the solution approximates to 1

8 0

4 years ago

What is HB? Triangle Mid-segment Theorem

Scorpion4ik [409]

Answer:

HB = 13

Step-by-step explanation:

In triangle GHJ, points A, B, C are mid points of the sides GH, HJ, GJ respectively.

Therefore by Mid-segment Theorem.

$AC = \frac{1}{2} HJ \\ \\ 3y - 5 = \frac{1}{2} (4y + 2) \\ \\ 3y - 5 = \frac{1}{2} \times 2 (2y + 1) \\ \\ 3y - 5 = 2y + 1\\ \\ 3y - 2y = 5 + 1 \\ \\ y = 6 \\ \\ HJ = 4y + 2 \\ \\ HJ = 4 \times 6 + 2 \\ \\ HJ = 24 + 2 \\ \\ HJ = 26 \\ \\ HB= \frac{1}{2} HJ \\ \\ HB= \frac{1}{2} \times 26 \\ \\ \huge \red{ \boxed{ HB= 13}}$

7 0

3 years ago

How do I do this? Please explain and show me.

galina1969 [7]

HOW DO YOU INSERT THE IMAGE I AN HELP BY DOING THAT

4 0

4 years ago