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Out of the total pens, 10% of pens are black. 10% of remaining pens are blue. 20% of remaining pens are red. The remaining 648 pens are green. How many total pens are there?

Out of the total pens, 10% of pens are black. 10% of remaining pens are blue. 20% of remaining pens are red. The remaining 648 pens are green. How many total pens are there? Correct Answer 1000

Let total number of pens be n.

Given,

10% of pens are black,

Number of black pens = (10/100)n = n/10

Remaining number of pens = n - n/10 = 9n/10

Given,

10% of remaining pens are blue,

Number of blue pens = (10/100) × (9n/10) = 9n/100

Remaining number of pens = 9n/10 - 9n/100 = 81n/100

Given,

20% of remaining pens are red,

Number of red pens = (81n/100) × (20/100) = 81n/500

Remaining number of pens = 81n/100 - 81n/500 = 81n/125

Given,

The remaining pens are green = 648

⇒ 81n/125 = 648

⇒ 81n = 648 × 125

⇒ n = 1000

∴ Total number of pens are 1000.

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