Answer:
Total Number of marbles present initially = 30 + 10 = 40 marbles
Let 'x' number of red marbles be added to the jar.
→ Total number of marbles = 40 + x
→ Number of Red marbles = 10 + x
We know that percentage of red marbles present be 60%. Therefore the remaining 40% is green marbles.
According to the question, we only add red marbles. So the number of green marbles remains the same. Therefore we get that,
→ 40% of ( 40 + x ) = 30
→ 40 ( 40 + x ) / 100 = 30
→ 1600 + 40 x = 30 × 100
→ 40 x = 3000 - 1600
→ 40 x = 1400
→ x = 1400 / 4
→ x = 35
Therefore 35 red marbles must be added to make the jar have 60% of red marbles.
