Examples for 8th grade - page 40

Comparing powers
How many times is number 5⁶ larger than number 4⁶?
Cars
Cars started at 7:00 AM. From point A car run at 40 km per hour, from B car run 70 km per hour. Between A and B is 250 km long road. When and where will meet (measured from point A)?
Base
Base of building is circle with diameter 25 m. Calculate the circumference of a circular trench witch diameter is 41 cm wider than the diameter of the base.
Slope
What is the slope of the line defined by the equation -2x +3y = -1 ?
Cylinder
The cylinder surface is 922 dm², its height is equal to the radius of the base. Calculate height of this cylinder.
Concentric circles
In the circle with diameter 19 cm is constructed chord 9 cm long. Calculate the radius of a concentric circle that touches this chord.
Salary
Mr. Johnson's had monthly salary 955 USD since the beginning of year. From which month his salary was increased by 52 USD, when in year earned 11824 USD (enter as a number from 1 to 12)?
BW-BS balls
Adam has a full box of balls that are large or small, black or white. Ratio of large and small balls is 5:3. Within the large balls the ratio of the black to white is 1:2 and between small balls the ratio of the black to white is 1:8 What is the ratio of.
Medal
Calculate the approximate weight of the gold Olympics medal, if its diameter is 8 cm and a thickness 6 mm. The density of gold find out in the tables or on the Internet.
Three numbers
The sum of the three numbers is 287. These numbers are in a ratio of 3: 7: 1/4 Define these numbers
Secret number
Determine the secret number n, which reversed decrease by 16.4 if the number increase by 16.4.
Two boxes-cubes
Two boxes cube with edges a=38 cm and b = 81 cm is to be replaced by one cube-shaped box (same overall volume). How long will be its edge?
Motion 2
At 10 o'clock started from place A car speed at 90 km/h. 20 minutes after started from the place B at speed 60 km/h another car. Distance places A and B is 120 kilometers. What time and where they meet?
Daughters
The man conducting the census asks a woman to age of three daughters. Woman says when multiply the age getnumber 72; if their ages add up, get a number of our house, as you see. The man says: That is not enough to calculate their ages. She says: my oldes
Nuts, girl and boys
Milena collected fallen nuts and called a bunch of boys let them share. She took a condition: the first boy takes one nut and tenth of the rest, the second takes 2 nuts and tenth new rest, the third takes 3 nuts and tenth new rest and so on. Thus managed.
Equator
Suppose that tourist went on foot over the Globe equator. How many meters more track made his hat on his head as the shoes on your feet? The radius of the earth is 6378 km and height of the tourist is 1.7 m.
Acute angles
Sizes of acute angles in the right-angled triangle are in the ratio 1: 3. What is size of the larger of them?
Digging companies
Company A would dig a pit for 12 days, company B for 15 days, company C for 20 days and the company D for 24 days. Work began together companies C and D, but after three days joined them other two companies. How long took to dig a pit?
Freight and passenger car
The truck starts at 8 pm at 30 km/h. Passenger car starts at 8 pm at 40 km/h. Passenger arrives in the destination city 1 hour and 45 min earlier. What is the distance between the city of departure and destination city?
For thinkings
The glass cube dive into the aquarium, which has a length of 25 cm, width 20 cm and height of 30 cm. Aquarium water rises by 2 cm. a) What is the volume of a cube? b) How many centimeters measure its edge?

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