Examples for 8th grade - page 26
- Tank No 8
Tank is filled by one inlet valve with a flow rate of 12 liters per second in 72 minutes. How long take the tank to fill, if we open half an hour after one more inlet?
First day got off 1/4 water from full container, second day 1/5 of the remaining water. How many percent remain container filled?
- Equation with fractions
Solve equation: ? It is equation with fractions.
- Alcohol 2
Two types of alcohol one 70% and second 61% give 11 liters of 57% alcohol. How many liters of each type are in the mixture?
Calculate the length of the Thales' circle described to right triangle with hypotenuse 44 cm.
How heavy must prepare bread at a bakery if lose during baking 14% of water and after baking must have 1.6 kg? (Calculate to the nearest gram)
The cuboid has a surface area 8710 cm2, the length of its edges are in the ratio 3:2:1. Calculate the volume of the cuboid.
- Barrel with liquid
Barrel with grain weight 263 kg. When it shed 43% of grain, ha weight 170 kg. What is the weight of empty barrel?
- Triangle angles
The angles α, β, γ in triangle ABC are in the ratio 10:5:6. Calculate size of angles.
- Apples in baskets
Determine how many apples are in baskets when in the first basket are 4 apples, and in any other is 29 apples more than the previous, and we have eight baskets.
- Grass garden
Mr. Grass would itself be mowed garden for 5 hours. His son Michael could do it for 7 hours. They agreed that they wake up at 5 am and begins to mow together. Ms. Grass needs drive into town at 8.30. Michael says that at that time they're done with work..
- Trrops - soldiers
Food stocks will last 20 soldiers of the 4-day training. How many days they could extend training if four soldiers become sick?
- Floating floor
In the new building is considered a floating floor worker in each room. 30 minutes lay 9 m2 of the floor. How long 3 workers laid the floor in 4 rooms with a total area of 90 m2?
- Father and son
Father is three times older than his son. 12 years ago father was nine times older than the son. How old are father and son?
- Comparing powers
How many times is number 55 larger than number 45?
How many cubic centimeters of wood sawdust is created by cut the tree trunk with a diameter of 38 cm and when the gap width is 6 mm?
- Homework - jumps
Sasha jumped 142 cm Peter 4 cm more than Jirka. Jirka 6 cm less than Misha. Misha 7 cm less than Filip and Filip half as much Sasha and Petr together. How far each jumped?
Mr. Peter build a pool shape of a four-sided prism with rhombus base in the garden. Base edge length is 6 m, distance of the opposite walls of the pool is 5 m. Estimated depth is 193 cm. How many hectoliters of water consume Mr. Peter to fill the pool?
First paver pave pavement for 33 hours. Second for 24 hours. Started first paver and after 5 hours, join the second. How long will they finish pavement?
We must dilute 80 liters of 7.6% aqueous vinegar to 4.2% one. How much water is necessary to add?