Answer:
There will be 21 blue marbles
Step-by-step explanation:
In a bag are blue, green and red marbles. Let x be the number of all marbles in the bag.
50% of all marbles are blue. 50% is exactly half of the marbles, so there are [tex]\frac{x}{2}[/tex] blue marbles.
30% of all marbles are green, so there are [tex]x\cdot 0.3=0.3x[/tex] green marbles.
The rest marbles are red marbles, so there are [tex]x-\frac{1}{2}x-0.3x=x-0.5x-0.3x=0.2x[/tex] red marbles.
There are 6 red marbles in the bag, thus
[tex]0.2x=6\\ \\2x=60\\ \\x=30[/tex]
Hence, there are
If you increase the number of blue marbles by 40%, then
15 - 100%
x - 140% (increased by 40%)
Write a proportion:
[tex]\dfrac{15}{x}=\dfrac{100}{40}[/tex]
Cross multiply:
[tex]100x=15\cdot 140\\ \\100x=2,100\\ \\x=21[/tex]
