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In a library, the ratio of science books to commerce books is 7 : 2, the total number of science books being 1001. When a new lot of science books were added to the library collection, the ratio of science books to commerce books changed to 50 : 13. What is the number of new science books in the lot?

In a library, the ratio of science books to commerce books is 7 : 2, the total number of science books being 1001. When a new lot of science books were added to the library collection, the ratio of science books to commerce books changed to 50 : 13. What is the number of new science books in the lot? Correct Answer 99

Let the number of Science and Commerce books be 7x and 2x respectively

According to the question, 7x = 1001

⇒ x = 143

∴ Number of commerce books = 2x = 286

When ‘n’ new books were added,

New ratio = 50 : 13

⇒ (1001+ n)/286 = 50/13

⇒ 13013 + 13n = 14300

⇒ 13n = 1287

⇒ n = 1287/13 = 99

∴ n = 99

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