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2 years ago

Bob the builder is making 480 kg of concrete mix

Mathematics

2 answers:

Marina CMI [18]2 years ago

6 0

Answer:

180 kg

Step-by-step explanation:

The ratio is

cement : sand : gravel

1 : 3 : 4

If he used 1 kg cement, 3 kg sand, and 4 kg gravel, he'd get 8 kg of concrete.

He wants to make 480 kg of concrete.

480/8 = 60

He needs 60 times more concrete than the numbers in the ratio.

60 * 3 kg = 180 kg

Answer: 180 kg

svetoff [14.1K]2 years ago

4 0

Answer:

If sand is 3 in the ratio, it is 180kg

Step-by-step explanation:

480/8=60 60 times 3 is 180

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Write down the first three terms of the sequence whose nth term is given by 2n-5

likoan [24]

Answer:

- 3, - 1, 1

Step-by-step explanation:

To find the first 3 terms substitute n = 1, 2, 3 into the formula

a₁ = 2(1) - 5 = 2 - 5 = - 3

a₂ = 2(2) - 5 = 4 - 5 = - 1

a₃ = 2(3) - 5 = 6 - 5 = 1

The first 3 terms are - 3, - 1, 1

6 0

2 years ago

The price of an item yesterday was $160 . Today, the price fell to 104 . Find the percentage decrease.

babymother [125]

The percentage drop would be 35%

6 0

2 years ago

How do you work out (7x+3)(7x-3)

spin [16.1K]

We can solve this using the FOIL method.

= (7x + 3)(7x - 3)

= (7x * 7x) + (7x * -3) + (3 * 7x) + (3 * -3)

= 49x - 21x + 21x - 9

= 49x - 9

Hope This Helped! Good Luck!

7 0

2 years ago

Solve the matrix equation for a, b, c, and d. [1 2] [a b] [6 5][3 4] [c d]= [19 8]

Anit [1.1K]

Answer:

The answer is " $\bold{\left[\begin{array}{cc}a&b\\c&d\end{array}\right] = \left[\begin{array}{cc}7&-2\\ -\frac{1}{2}&\frac{7}{2}\end{array}\right]}$ ".

Step-by-step explanation:

$\bold{\left[\begin{array}{cc}1&2\\3&4\end{array}\right] \left[\begin{array}{cc}a&b\\c&d\end{array}\right] = \left[\begin{array}{cc}6&5\\ 19&8\end{array}\right]}$

Solve the L.H.S part:

$\left[\begin{array}{cc}1&2\\3&4\end{array}\right] \left[\begin{array}{cc}a&b\\c&d\end{array}\right]\\\\\\\left[\begin{array}{cc}a+2c&b+2d\\3a+4c&3b+4d\end{array}\right]$

After calculating the L.H.S part compare the value with R.H.S:

$\left[\begin{array}{cc}a+2c&b+2d\\3a+4c&3b+4d\end{array}\right]= \left[\begin{array}{cc}6&5\\ 19&8\end{array}\right]} \\\\$

$\to a+2c =6....(i)\\\\\to b+2d =5....(ii)\\\\\to 3a+4c =19....(iii)\\\\\to 3b+4d = 8 ....(iv)\\\\$

In equation (i) multiply by 3 and subtract by equation (iii):

$\to 3a+6c=18\\\to 3a+4c=19\\\\\text{subtract}... \\\\\to 2c = -1\\\\\to c= - \frac{1}{2}$

put the value of c in equation (i):

$\to a+ 2 (- \frac{1}{2})=6\\\\\to a- 2 \times \frac{1}{2}=6\\\\\to a- 1=6\\\\\to a =6 +1\\\\\to a = 7\\$

In equation (ii) multiply by 3 then subtract by equation (iv):

$\to 3b+6d=15\\\to 3b+4d=8\\\\\text{subtract...}\\\\\to 2d = 7\\\\\to d= \frac{7}{2}\\$

put the value of d in equation (iv):

$\to 3b+4 (\frac{7}{2})=8\\\\\to 3b+4 \times \frac{7}{2}=8\\\\\to 3b+14=8\\\\\to 3b =8-14\\\\\to 3b = -6\\\\\to b= \frac{-6}{3}\\\\\to b= -2$

The final answer is " $\bold{\left[\begin{array}{cc}a&b\\c&d\end{array}\right] = \left[\begin{array}{cc}7&-2\\ -\frac{1}{2}&\frac{7}{2}\end{array}\right]}$ ".

4 0

3 years ago

Pls need answer fast

galina1969 [7]

Answer:

Step-by-step explanation:

The answer is B

5 0

2 years ago