Ques:- The average age of 12 students is 20 years. If the age of one more student is included, the average decreases by 1. What is the age of the new student?
A. 5 years
B. 6 years
C. 7 years
D. 9 years
Ques:- Gold is 19 times as heavy as water and copper is 9 times. In what ratio should these metals be mixed so that the mixture may be 15 times as heavy as water?
A. 2 : 1
B. 3 : 2
C. 4 : 3
D. 5 : 4