# Examples for 9th grade - page 14

- Pizza

A school survey found that 9 out of 16 students like pizza. If 5 students are chosen at random, what is the probability that all 5 students like pizza? - Combinatorics

The city has 10 fountains. Works only 7. How many options are there that can squirt ? - Train and car

The train and the car started at a constant speed to journey. When the train travels 78 km, the car travels 64 km. How many km travels the train when the car travels 78 km? - Waiting room

In the waiting room are people and flies. Together they have 15 heads and 50 legs (fly has 6 legs). How many people and flies are in the waiting room? - Sea water

Seawater contains about 7% salt. How many dm^{3}of distilled water we must pour into 14 dm^{3}of sea water to get water with 1.7% salt? - Reciprocal

What is the reciprocal of the sum of the reciprocals of 7 and 2? - Parachutists

Parachutists during freefall firstly held in groups of 4, then of 6, then 9, 12 and finally of 18 members. How many parachutists jump at least should be, if at each group must all be involved. - Five tractors

Five tractors plow field in 4.8 hours. How long plow this field if after 1.5 hours of work two tractors went to a different field? - Workman - shift

The worker produces 300 components per shift. How many components would be produced in 18 shift, if his performance gradually increased every shift by 3 components? - 4s pyramid

Regular tetrahedral pyramid has a base edge a=6 and collaterally edge length b=15. What is its height? - Sand pile

Auto sprinkled with sand to approximately conical shape. Workers wanted to determine the volume (amount of sand) and therefore measure the circumference of the base and the length of both sides of the cone (over the top). What is the volume of the sand c - Win in raffle

The raffle tickets were sold 200, 5 of which were winning. What is the probability that Peter, who bought one ticket will win? - Ladislav in Amsterdam

Ladislav was reward and went to conference in Amsterdam. Conferense fee was € 2184. Calculate how many books Ladislav could buy at the price of 42 and 28 euros if he don't want fill whole home library and he can buy only 63 books? - Chess

How many ways can select 3 fields on classic chess board with 64 fields, so that fields don't has the same color? - Olympics metals

In how many ways can be win six athletes medal positions in the Olympics? Metal color matters. - Gold coin

Gold coin contains 963 promile pure gold, which is 8.39 g. What is the weight of coin in grams? - Angles in a triangle

The angles of the triangle ABC make an arithmetic sequence with the largest angle γ=69°. What sizes have other angles in a triangle? - Arm

Calculate the length of the arm r of isosceles triangle ABC, with base |AB| = 16 cm and a height v=10 cm. - Mrak - cloud

It is given segment AB of length 12 cm, where one side of the square MRAK laid on it. MRAK's side length 2 cm shown. MRAK gradually flips along the line segment AB the point R leaves a paper trail. Draw the whole track of point R until square can do the. - Two pumps

The first pump fills the tank in 24 hours second pump in another 40 hours. For how long will take fill the tank if operate both pumps at the same time?

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