a bag of marbles contains 5 red,7 green ,and some blue.if 1/3 of the marbles in the bag are blue,how many blue marbles are in the bag?

If there are only red, green and blue marbles in the bag, then given that 1/3 are blue, then red and green occupy 1-1/3=2/3 of the bag.

Use direct proportion:

2/3 bag : 5+7=12
1/3 bag : X
Cross multiply:
x=(1/3)*12÷(2/3)
=12/2
= 6 (blue marbles)

A rectangular block of aluminium 24 cm long and 12cm wide is melted and recast into cubes of edge 4 cm. 64m of aluminium is lost during the process. If 125 cubes are obtained calculate the height of the rectangular block before it was melted

To find the number of blue marbles in the bag, we first need to determine the total number of marbles in the bag.

We are given that 1/3 of the marbles in the bag are blue. This means that the remaining 2/3 of the marbles are red and green.

Let's calculate the total number of marbles in the bag using the information provided:

Total number of marbles = Number of blue marbles + Number of red marbles + Number of green marbles

Since we know that there are 5 red marbles and 7 green marbles, we can substitute those values into the equation:

Total number of marbles = Number of blue marbles + 5 + 7

However, since we want to find the number of blue marbles, we can rewrite the equation as:

Number of blue marbles = Total number of marbles - 5 - 7

To solve for the total number of marbles, we can set up the equation:

2/3 * Total number of marbles = Total number of marbles - 5 - 7

Now, let's solve for the total number of marbles:

2/3 * Total number of marbles = Total number of marbles - 12
Multiply both sides of the equation by 3 to get rid of the fraction:

2 * Total number of marbles = 3 * (Total number of marbles - 12)
Distribute the 3 on the right side of the equation:

2 * Total number of marbles = 3 * Total number of marbles - 36
Subtract Total number of marbles from both sides of the equation:

2 * Total number of marbles - 3 * Total number of marbles = -36
Simplify:

-Total number of marbles = -36
Divide both sides of the equation by -1:

Total number of marbles = 36

Now, substitute this value back into the equation to find the number of blue marbles:

Number of blue marbles = 36 - 5 - 7
Number of blue marbles = 24

So, there are 24 blue marbles in the bag.