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Algebra

The use of letters to substitute unknown numbers to form an equation. Solve the equation to get the unknown number using different methods such as simultaneous equations and more.

500 Questions

Lawful brakes must stop a car at 20 miles per hour within how many feet?

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These rules vary somewhat from state to state.

In California, passenger car brakes must stop a vehicle going 20 MPH within 25 feet.

A radio controlled car rolls 10 miles south then reverses direction and rolls 8 miles north The car has traveled a distance of 18 miles and has a displacement of miles south?

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The car has traveled a total distance of 18 miles (10 miles south + 8 miles north), but its displacement is 2 miles south. Displacement is the shortest distance between the starting and ending points, regardless of the actual path taken.

How many minutes to travil 29 miles?

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The time it takes to travel 29 miles will depend on the speed at which you are traveling. For example, if you are driving at 60 miles per hour, it would take approximately 29 minutes to travel that distance. To calculate the exact time, you can divide the distance by the speed at which you are traveling.

Find the Distance between 2 2 5 -1?

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To find the distance between two points in 3D space (x1, y1, z1) and (x2, y2, z2), use the distance formula: Distance = sqrt((x2 - x1)^2 + (y2 - y1)^2 + (z2 - z1)^2)

Substitute the coordinates into the formula to find the distance.

What is the ratio of 11 to 132?

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11:132 :: 1:12

Does sine 40 equal sin 20?

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NO!!!

Sine40 = Cosine50 = 0.64278...

Sin30 = Cos 60 = 0.5

Sin 0 = Cos 90 = 0

Sin 90 = Cos 0 = 1

From Latin the word 'Sine' means 'curve'. Cosine means 'Complimentary Sine' or Complimentary curve'.

The 'awkward' decimal numbers are based on a the radius of a circle, that radius being the hypotenuse of a right- triangle based at the circles origin/centre.

What does a number followed by a letter in algebra mean?

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It means multply

e.g. 5a means '5' multiplied to the value of 'a'.

As in all multplied/addition.

3+3+3+3+3 = 5 X 3 = 15

Instead of writing all the plusses , we shorten it to multiply.

Similarly

a + a +a + a + a = 5 X a = 5a

In algebra the multiplication sign (x) is never shown as it may be confused with the unknown 'x'.

In algebra

addition is shown as 'a + b

subtraction is shown as 'a - b' .

multiplication is shown as 'ab'

division is shown as 'a/b' ( like an fraction).

The tens digit of a number is six more than the ones digit?

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No. The tens unit is independent of the ones unit

Square root of 160?

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sqrt(160)

We know that 12^2 = 144 and 13^2 = 169 .

So the square roots of 144 and 169 are 12 & 13 respectively,

Since 160 is between 144 & 169 , then its square root is between 12 & 13.

So by trial and Error , we try 12.5^2 = 156.25 This is too small so try 12.6

12.6^2 = 158.76 Still too smalle

12.7^2 = 161.29 This is too large , so try 12.68

12.68^2 = 160.7824 Still too large ,so try 12.67^2

12.67^2 = 16.5289 Too large

12.66^2 = 160.2756

12.65^2 = 160.0225

12.649^2 = 159.99

12.6495^2 = 160.0098503...

So to 4 d.p. the sqrt(160) ~ 12.6495

You can keep going like this, until you reach the required number of decimal places.

There is a 'mechanical' method to find square root, but it would take me all day to explain .

Per electronic calculator the answer is 12.64911064....

How do you turn 0.04 into a fraction?

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To convert any terminating decimal to a fraction, inspect the number of decimal digits. In this case it is '2'

So place the decimal over 'one point and two zeroes)

Hence

0.04 / 1.00

Cancel down the decimal point

004/100

The prefix zeroes to '4' can be ignored.

Hence

4/100

Cancel down by '4' Hence

'1/25'. THe Answer!!!!!

NB There is a different technique for rational decimals to inifinity.

NNB Irrational decimals CANNOT be converted to an exact quotient(fraction).

Where does Pythagorean come from?

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'Pythagorean' is the 'adjective for 'Pythagoras'.

{ythagoras was a Classical Greek mathematician who gave us the equation

h^2 = a^(2) + b^(2) .

In words, 'The square of the hypotenuse(h) is equal to the sum of the other two sides squared'.

NB This only applies to 'right-angled' triangles (trigons).

Find the equation of the line joining the point -76-3 and 7-63?

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First find the slope 'm'

m = ( y(1) - y(2))/ (x(1) - x(2))

Hence

m = ( -3 - - 63) / ( -76 - 7)

m = 60/ -83 = -60/83

Hence

y = (-60/83)x + c

To find 'c' take either point and displace against x & y.

Hence

y - - 3 = ( -60/83) (x - -76)

y + 3 = (-60/83) ( x + 76)

Multiply through by '83'.

Hence

83y + 249 = -60x - 4560

83y = -60x - 4809

or

60x + 83y = -4809

or

60x + 83y + 4809 = 0

Five to the fifth power over five to the forth power?

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5^(5) / 5^(4) = 5^(5-4) = 5^(1) = 5

or

5^(5) /5^(4)= 5x5x5x5x5 / 5x5x5x5

Cancel down by '5' ( top and bottom) and we are left with 5/1 = 5 as before.

NB We do normally show number to the power/exponent of '1' except to aid in exponential calculations.

What kind of number is 0.5?

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It is a decimal number used to give an answer to a question like: What Is half of 1? Which is simply 0.5

How do you find cubed root of 1728 with working?

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We know that the cube of 10 is 10^(3) = 1000

So try 11^(3) = 1331 (Too low)

So try 12^(3) = 1728 THE ANSWER!!!! Go No futher.

So the cube root (1728) = 12

Can you take the square root of a negative number?

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NO!!!!

sqrt(-n) ?????

However,

-n X -n = (+)n^2

Sqrt(n^2) = either -n or (+)n , because either -n X -n = (+)n^2 or n x n = n^2

However,

sqrt(-n) takes us into IMAGINARY numbers.

sqrt(-n) = sqrt( -1 x n) = sqrt(-1) X sqrt(n)

.The sqrt(-1) is mathemtically unresolved and is given the symbol 'i' (small / lower case letter 'i'.

The sqrt(n) .being positive can be found.

What is -n plus 4n?

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-n + 4n = 4n - n = 3n Done!!!!!

Find the value or values of y in the quadratic equation y to the second power plus 4y plus 4 equals 7?

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y^2 + 4y + 4 = 7

Hence

y^2 + 4y -3 = 0

Apply the Quadratic Eq'n

y = { - 4 +/- sqrt[(4)^(2) - 4(1)(-3)]} / 2(1)

y = { -4 +/- sqrt[ 16 + 12]} / 2

y = { 4 +/- sqrt(28)]}/ 2

y = {4 +/- 5.2915....} /2

y = 9.2915/// / 2 = 4.64575....

&

y = -1.2915... / 2 = -0.64575....

What is the total amount of money owed if 1250 was borrowed for four years at 3.5 interest?

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Assuming Compound Interest

I(n) = I(o)[1 + r/100]&(n)

Where

I(o) = 1250

r = 3.5%

n = 4 years

Substitutie

I(4) = 1250[1 + 3.5/100]^(4)

Hence

I(4) = 1250 [ 1.035]^(4)

I(4) = 1250[1.147523]

I(4) = 1434.40 is the total amount owed.

NB Compound interest is the usual business practice of calculating interest.

NNB Payment would possibly be done on an monthly basis ; 1434.40 / 48 = 29.88 is paid each month .

What is the answer to a x a x a plus b x b x b equals c x c x c?

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well it could be anything, but I think you are thinking of Pythagoras' theorem.

a(2) x b(2) = c(2) (2) = squared

What is the reciprocal of .66?

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Divide 1 by 0.66: 1/ 0.66 = 1.51515151515

Where does the graph cross the y axis at in y equals 5x-2?

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y = 5x - 2

This follows the general equation for a straight line y = mx + c.

Where 'm' is the slope/gradient and 'c' is the y-intercept.

At the point the line crosses the y-axis , then x = 0

Hence

y = 5(0) - 2

y = -2 is the point the line intercept the y-axis.

A polygon with all sides congruent is?

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A giant ladybug!* * * * *

Oh, that is soooo funny!

The correct answer is equilateral. If all the angles are also congruent, then the polygon is said to be regular.

What is the definition of a zero exponent?

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Any value with a 'zero' exponent is equaL TO '1'.

A^(0) = 1

proof

Let a^(0) =.

a^(n - n) = a^(n) / a^(n) Cancel down by a^(n) hence it equals '1'.