The average age of 30 students is 9 years. If the age of their teacher is included, the average age become 10 years. The age of the teacher ( in years ) is

Study the information carefully to answer the question that follow.
In a college there are 900 students who are doing Post Graduation (PG) in any one of the subjects, out of five different subjects, out of the five different subjects viz. Zoology, Botany, Mathematics, Physics and Statistics. The ratio between the boys and the girls among those is 5:4 respectively, 20% of the total girls are doing PG in Zoology and 25% of the total girls are doing PG in Statistics. Total number of students doing PG in Botany is 220. Total students who are doing PG in Mathematics is 150. Respectively ratio between the number of girls and the number of boys doing PG in statistics is 2:3. Twenty percent of the total number of boys are doing PG in Mathematics is 1:2 respectively. There are equal number of boys and girls who are doing PG in PG in Physics. 180 students are doing PG in Zoology.
What is the respective ratio between the boys doing PG in Mathematics and the number of girls doing PG in Botany?

The bar graph shows the number of painting sold an art gallery in each month from January to June.

 How many paintings does it need to sell in July for the 7 month average to be 90?

Excluding stoppages, the speed of a train is 120 kmph and including stoppage, it is 50 kmph. For how many minutes does the train stop per hour?

If a sum of money becomes 8 times in 9 years at compound interest annually, in how much time it will become 32 times?

If ( 2x – y): ( 5x+3y)=3 : 8 then ( x² + y²) : ( x² – y²)=?