1.  In a note collection, there is one new ₹2000 note for every three old ₹500 notes. 10 more new ₹2000 notes are added to the collection and the ratio of new ₹2000 notes to old ₹500 notes would be 1: 2. Based on the information, the total number of notes in the collection now becomes?
A. 60
B. 30
C. 70
D. 90

Answer: Option D

Explanation:

Let 'x' be the number of new ₹2000 notes.

Given for one new 2000 note there are three old 500 notes.

=> 3x

Given 10 more new ₹2000 notes are added to the collection and the ratio of new ₹2000 notes to old ₹500 notes

=> x + 10 /3x = 1/2 => x = 20

Therefore, number of new ₹2000 notes => x+10 = 30.

Old ₹500 notes => 3x = 60.

Thus, the total number of notes in the collection => 30 + 60 = 90.