High School

DIFFICULT MATHS

Red counters : Green counters : Blue counters = 3 : 4 : 5

15 red counters and some blue counters are added to the bag. The ratio after this is shown below:

Red counters : Green counters : Blue counters = 7 : 6 : 8

Work out the total number of counters in the bag after the red and blue counters were added.

Answer :

After adding 20 blue counters to the initial 15 red counters, the total number of counters in the bag is 61 counters.

Given:

Initial ratio of red, green, and blue counters = 3 : 4 : 5

Total number of red counters initially = 15

Total number of red counters after addition = 15

Let's denote the number of blue counters added as 'b'.

After the addition, the ratio becomes:

7 : 6 : 8

Now, let's find the ratio of red counters before and after the addition:

Initial red counters : Final red counters

3 : 7

Since the ratio of red counters remains the same, we can write the equation:

[tex]\( \frac{15}{3} = \frac{15 + b}{7} \)[/tex]

Cross multiply to solve for 'b':

[tex]\( 15 \times 7 = 3 \times (15 + b) \)[/tex]

[tex]\( 105 = 45 + 3b \)[/tex]

[tex]\( 3b = 105 - 45 \)[/tex]

[tex]\( 3b = 60 \)[/tex]

[tex]\( b = \frac{60}{3} \)[/tex]

[tex]\( b = 20 \)[/tex]

So, 20 blue counters were added.

Now, let's find the total number of counters after the addition:

Total red counters = 15 + 15 = 30

Total blue counters = 20

Total green counters = (6/7) * Total red counters = [tex]\( \frac{6}{7} \)[/tex] * 30 = 25.71 (approximated to nearest integer)

However, since the number of counters must be a whole number, let's adjust the green counters:

Let's consider the ratio:

[tex]\( \frac{7}{6} = \frac{30 + g}{25.71} \)[/tex]

Solving for 'g':

[tex]\( 7 \times 25.71 = 6 \times (30 + g) \)[/tex]

[tex]\( 179.97 = 180 + 6g \)[/tex]

[tex]\( 6g = 179.97 - 180 \)[/tex]

[tex]\( 6g = -0.03 \)[/tex]

[tex]\( g = \frac{-0.03}{6} \)[/tex]

[tex]\( g = -0.005 \)[/tex]

Since 'g' is negative, it implies there are fewer green counters than in the initial ratio. So, let's adjust the green counters to 26.

Now, the total number of counters:

Total red counters = 30

Total green counters = 26

Total blue counters = 20

Total counters in the bag = 30 (red) + 26 (green) + 20 (blue) = 76 counters

So, there are 76 counters in the bag after the red and blue counters were added.