Ramu reads 15th pages of a book. If she reads further 40 pages, she would have read  7/10th page of the book. How many pages are left to be read?

Let the total number of pages be x.

Number of pages read by Ramu = ¹/₅ x

If she reads 40 more pages,

Total number of pages read = ¹/₅ x + 40

Given: ⁷/₁₀ x = ¹/₅ x + 40

= ⁷/₁₀ x − ¹/₅ x = 40

= (^{7x − 2x})/10 = 40

= ^5x/₁₀ = 40

= x/2 = 40

= x = 80

Hence, the required number of pages = 80.