Exams

Gitanjali Rao, an 11-year-old Indian-American schoolgirl, was named as "America’s top young scientist" for inventing a cost-effective, quick lead-contamination detector in water. The seventh-grade student was inspired by the large-scale lead contamination in water in Flint, Michigan, that came to light recently.

15 girls are absent => b = 2(g-15)...... eqn...(1)

45 boys are absent => g - 15 = 5(b-45).....eqn...(2)

=> g = 5(b-45) + 15

=> b = 2((5(b-45)+15)-15)

=> b = 2(5b - 225 + 15 - 15)

=> b = 2(5b-225)

=> b = 10b - 450

=> 9b = 450

=> b = 50

so from equation(2)

g - 15 = 5(b - 45)

=> g - 15 = 5(50-45)

=> g - 15 = 5(5)

=> g = 25 + 15

=> g = 40

Therefore, the number of boys = 50 and girls = 40

let, speed of Ali=X mph and Faizer=Y mph

Now, relative speed when Ali is walking int the same direction with Faizer= (X-Y)mph
hence, according to question, 27/(X-Y)=9 ; solving X-Y=3; --- (1)

Now relative speed when walking in the opposite direction= (X+Y) mph
hence, according to question, 27/(X+y)=3; solving X+Y=9; --- (2)

solving 1 and 2 we get X=6 and Y=3, where X is the speed of Ali.

Sum of ages of husband, wife and child= (24 × 3) + 9 = 81 years

Sum of ages of wife and child => 25 × 2 + 10 = 50 + 10 = 60 years

Age of husband = 81 - 60 = 21 years.

The pharynx is a passageway shared by both food and air.