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3 years ago

Sam and Mary collect marbles. “If you give me 5 marbles I’ll have twice as many as you.” said Sam to Mary.

Mathematics

1 answer:

ivann1987 [24]3 years ago

7 0

Answer:

54 marbles

Step-by-step explanation:

The question is a word problem leading to a simultaneous equation

Let 'x' represent the initial number of marbles with Sam, and let 'y' represent the initial number of marbles with Mary,

If Mary gives Sam 5 marbles, we have;

x + 5 = 2 × (y - 5)...(1)

If Sam gives Mary 4 marbles, we get;

x - 4 = y + 4...(2)

From equation (1), we get;

x + 5 = 2 × (y - 5) = 2·y - 10

x = 2·y - 10 - 5 = 2·y - 15

x = 2·y - 15...(3)

From equation (2), we have;

x - 4 = y + 4

∴ x = y + 4 + 4 = y + 8

x = y + 8...(4)

Equating the two values of 'x' in equation (3), and equation (4), we get;

2·y - 15 = y + 8

2·y - y = 8 + 15 = 23

∴ y = 23

From equation (4), we get;

x = y + 8 = 23 + 8 = 31

x = 31

The total number of marbles they have altogether = x + y

However, x + y = 23 + 31 = 54

Therefore;

The total number of marbles they have altogether = 54 marbles.

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Answer:

Step-by-step explanation:

The question has typographical errors. The correct question is:

"A 12-foot ladder is leaning against a building. If the bottom of the ladder is sliding along the pavement directly away from the building at 3 feet/second, how fast is the top of the ladder moving down when the foot of the ladder is 5 feet from the wall?

Solution:

The ladder forms a right angle triangle with the ground. The length of the ladder represents the hypotenuse.

Let x represent the distance from the top of the ladder to the ground(opposite side)

Let y represent the distance from the foot of the ladder to the base of the wall(adjacent side)

The bottom of the ladder is sliding along the pavement directly away from the building at 3ft/sec. This means that y is increasing at the rate of 3ft/sec. Therefore,

dy/dt = 3 ft/s

The rate at which x is reducing would be

dx/dt

Applying Pythagoras theorem which is expressed as

Hypotenuse² = opposite side² + adjacent side², it becomes

x² + y² = 12²- - - - - - - -1

Differentiating with respect to time, it becomes

2xdx/dt + 2ydy/dt = 0

2xdx/dt = - 2ydy/dt

Dividing through by 2x, it becomes

dx/dt = - y/x ×dy/dt- - - - - - - - - - 2

Substituting y = 5 into equation 1, it becomes

x² + 5 = 144

x² = 144 - 25 = 119

x = √119 = 10.91

Substituting x = 10.91, dy/dt = 3 and y = 5 into equation 2, it becomes

dx/dt = - 5/10.91 × 3

dx/dt = - 1.37 ft/s

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4 years ago

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Gnom [1K]

Answer:

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3 years ago

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What is the surface area?

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$\large\bf{\underline{Answer:}}$

‎ ‎‎‎ ‎ ‎‎‎ ‎ ‎‎‎ ‎ ‎‎‎ ‎ ‎‎‎ ‎ ‎‎‎ ‎ ‎‎‎ ‎ ‎ $\large\bf{ = 3000 \:ft^2}$

__________________________________________

$\large\bf{\underline{Given:}}$

A 3 dimensional figure with 5 sides
it has 3 rectangles with dimensions 28 ft and 25 ft
And 2 triangles with base =30 ft and height = 20 ft

$\large\bf{\underline{To\: find:}}$

Total surface area of figure

$\large\bf{\underline{Therefore:}}$

$\bf{area \:of\: figure}$

‎ㅤ ${\bf = area \:of \:3\: rectangles + 2 \: triangles}$

$\large\bf{\underline{Formulas:}}$

$\boxed{\bf\pink{area\:of\: triangle= \frac{1}{2}\times base\times height}}$

$\boxed{\bf\pink{area\:of\: rectangle=length\times breadth}}$

‎ ‎‎‎ ‎ ‎‎‎ ‎ ‎‎‎ ‎ ‎‎‎ ‎ ‎‎‎ ‎ ‎‎‎ ‎ ‎‎‎ ‎ ‎ $\large\bf{= 3\times (28 \times 25 )+ 2(\frac{1}{2} \times 30 \times 20)}$

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‎ ‎‎‎ ‎ ‎‎‎ ‎ ‎‎‎ ‎ ‎‎‎ ‎ ‎‎‎ ‎ ‎‎‎ ‎ ‎‎‎ ‎ ‎ $\large\bf{=2400+ 600}$

‎ ‎‎‎ ‎ ‎‎‎ ‎ ‎‎‎ ‎ ‎‎‎ ‎ ‎‎‎ ‎ ‎‎‎ ‎ ‎‎‎ ‎ ‎ $\large\bf{= 3000}$

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$\large\bf{\underline{Hence,}}$

❒ Area of given figure

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rodikova [14]

Answer:

4x + 15

Step-by-step explanation:

Let the age of Khairul's uncle y.

From the question given above, the following were obtained:

Khairul's age = x years

In 5 years time:

Khairul's age = x + 5

Khairul's uncle age = y + 5

But from the question given above,

Khairul`s uncle will be 4 times as old as what khairul will be in 5 years. This can be written as follow:

y + 5 = 4(x + 5)

Clear bracket

y + 5 = 4x + 20

Subtract 5 from both side

y + 5 – 5 = 4x + 20 – 5

y = 4x + 15

Therefore, Khairul's uncle present age is 4x + 15

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