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Amiraneli [1.4K]
2 years ago
12

Which numbers between 10 and 99 have digits that differ by 4 and add to 6

Mathematics
1 answer:
madreJ [45]2 years ago
8 0

Answer:

A

Step-by-step explanation:

Correct option is A)

Let a 3-digit number ABC

Case (1)

If A=7, then B  and  C can be any digit but not 7

so, total 9 digits (0,1,2,3,4,5,6,8,9) can replace B and C

Then total such combinations =1(9)(9)=81

Case (2)

If B=7  then A can be any digit but not  0 and 7, because if A=0 it will be a 2-digit number.

And C can be any digit but not 7

Then total combinations =(8)(1)(9)=72

Case (3)

If C=7  then A can be any digit but not 0 and 7, because if A=0 it will be a 2-digit number.

And B can be any digit but not 7

Then total combinations =(8)(9)(1)=72

So, total numbers between 99 and 1000 which have exactly one of their digits as 7 are =81+72+72=225

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Element X decays radioactively with a half life of 9 minutes. If there are 760 grams of Element X, how long, to the nearest tent
ElenaW [278]

Answer:

Step-by-step explanation:

760·0.5^(t/9) = 19

0.5^(t/9) = 19/760

2^(-t/9) = 0.025

-t/9 = log₂(0.025)

t = -9log₂(0.025) = 47.9 minutes

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3 years ago
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Find all real values of x such that f(x) = g(x) <br>for f (x) = x^2 + 1 g(x) = 3x - x^2​
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Can the product of 4 and any number always be written as a sum of two equal addends
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Step-by-step explanation:

Example : 4 x 2 = 8

8 = 4×4

Thus proven YES.

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Y=3x-4;y=4+x substitution
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Step-by-step explanation:

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While visiting Wallawulla State​ Park, Joe approximated the angle of elevation to the top of a mound to be 40 degrees . After wa
katen-ka-za [31]

Answer:

Height of mound = 794 ft

Step-by-step explanation:

To illustrate the angle of elevation and distance, i have drawn it and attached below.

Now, from my diagram;

h = the height of the mound

At his first point of his trip to the foot of the mound, the angle of elevation is 40°, while the horizontal distance to the foot of the mound is "X"

So, by triangle definition,

tan(40°) = h/x

And so;

h = x tan40

h = 0.8391x  - - - - (eq 1)

At his second point of the trip to the foot of the mound, Joe is now,

"(x - 450) ft" from the foot of the mound.

Thus, his angle of elevation is 40 + 18 = 58°.

So, by triangle definition,

tan(58°) = h/(x - 450)

h = (x - 450)•(tan(58°))

h = 1.6003(x - 450)

h = 1.6003x - 720.135   - - - - -(eq2)

To get the height(h) of the mound, let's equate (eq1) to (eq2).

0.8391x = 1.6003x - 720.135

1.6003x - 0.8391x = 720.135

0.7612x = 720.135

x = 720.135/0.7612

x = 946.0523 ft

Let's put this value for x in eq (1);

h = 0.8391 x 946.0523 = 793.83 ft ≈ 794ft

4 0
3 years ago
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