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3 years ago

How many 2 digit whole numbers are increased by 18 when they're digits are reversed

Mathematics

1 answer:

Anika [276]3 years ago

8 0

This can be calculated easily.

As any two digit number can be written in the following form:

N= 10x +y

If we reverse the number now, it would become:

N' = 10y + x

So if we subtract one from the other, we should obtain 18 ( as mentioned in the question ).

N-N'= 18

=> x-y = 2

Thus, any number whose digits differ by two would be an aswer to the question.

The only numbers which satisfy this are : 13,24,35,46,57,68,79

But this would not be true for any 3 or more digit number.

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Find the total area for the regular pyramid.

hram777 [196]

Answer:

Option B

Step-by-step explanation:

Given is the hexagonal pyramid.

We know the radius of the base is same as its side.

Find the base area:

A = 3√3/2a²
A = 3√3/2*6² = 54√3

Given the height and radius, find the side of the lateral triangular faces:

$\sqrt{8^2+6^2} =\sqrt{100} =10$

Each of 6 triangles have sides 10, 10 and 6 units.

Find the area using heron's formula:

s = P/2 = (10*2 + 6)/2 = 13
s - a = s - b = 13 - 10 = 3
s - c = 13 - 6 = 7
$A = \sqrt{s(s-a)(s-b)(s-c)} =\sqrt{13*3*3*7} =3\sqrt{91}$

Total surface area:

$S = 6*3\sqrt{91}+54\sqrt{3} =18\sqrt{91}+54\sqrt{3}$

Correct choice is B

3 0

2 years ago

Simplify the expression 4(-8x+5)-(-33x-26)=

Pavel [41]

Answer:

x+46

Explanation:

4(−8x+5)−(−33x−26)

Distribute the Negative Sign:

=4(−8x+5)+−1(−33x−26)

=4(−8x+5)+−1(−33x)+(−1)(−26)

=4(−8x+5)+33x+26

Distribute:

=(4)(−8x)+(4)(5)+33x+26

=−32x+20+33x+26

Combine Like Terms:

=−32x+20+33x+26

=(−32x+33x)+(20+26)

=x+46

3 0

3 years ago

3. Arrange these numbers from least to greatest. -2.5 -1/3 1.7 27/4 -0.9

Svet_ta [14]

Answer: -2.5,, -0.9,, -1/3,, 1.7,, 27/4

Step-by-step explanation:

6 0

3 years ago

The speed of a boat in still water is 40 mph. If it takes the same time for the boat to travel 8 miles upstream as it does to tr

antoniya [11.8K]

Answer:

Current speed is 40mph

Step-by-step explanation:

We firstly need to know what is intended by upstream and downstream. When the boat travels in the direction of the current (horizontal movement of the water), we say it is moving downstream otherwise it is moving upstream.

Let's assume the speed of the boat is A and that of the current is B, then the speed when it moves dowstream would be A + B and the speed if it moves upstream would be A – B.

In this question, we know that the speed of the boat is 40mph. Given that it takes the same time to travel 8miles upstream as it does to travel 24miles downstream, we have

Speed upstream = 8/t

Speed downstream = 24/t

Respectively.

Let speed of current be X, then

Speed downstream = 40 + X

Speed upstream = 40 – X

From the question we have:

(40 + x)/24 = (40 – X)/8

(40 + x)/3 = (40 – x)/1

3(40 – x) = 40 + X

120 – 3x = 40 – X

120 – 40 = 3x – X

2x = 80

X = 40.

Therefore, current speed is 40mph

5 0

2 years ago

Please help me asap! The drop down menu contains: Square Units Cubic Units Units

qwelly [4]

Answer:

Just units

Step-by-step explanation:

Looking for perimeter, not area and volume

6 0

2 years ago