Examples for 8th grade - page 20
- Sea water
Seawater contains about 6.8% salt. How many dm3 of distilled water we must pour into 30 dm3 of sea water to get water with 1.9% salt?
- 4s pyramid
Regular tetrahedral pyramid has a base edge a=6 and collaterally edge length b=15. What is its height?
Camel owner wants to get out of the city into oasis. He bought 3000 bananas, which wants to sell in oasis. However oasis from the city divided 1,000 kilometers of desert. Camel can carry at one time up to 1000 bananas, and for every kilometer traveled, ea
- Maximum area of rhombus
Calculate the interior angles at which equilateral rhombus has maximum area.
- Chocholate pyramid
How many chocolates are in the third shelf when at the 8th shelf are 41 chocolates in any other shelf is 7 chocolates more the previous shelf.
- Construct 1
Construct a triangle ABC, a = 7 cm, b = 9 cm with right angle at C, construct the axis of all three sides. Measure the length of side c (and write).
In a completely crowded resort was 30% from the Czech Republic quarter visitors were from Slovakia and the rest 135 came from Germany. What capacity have resort?
- Three-digit numbers
How many three-digit numbers are from the numbers 0 2 4 6 8 (with/without repetition)?
- Four-digit number
Find also a four-digit number, which quadrupled written backwards is the same number.
- Divisible by 5
How many three-digit odd numbers divisible by 5, which are in place ten's number 3?
Suzanne helped write out diplomas. Issuance its first took 4 minutes, each next 2.4 minutes. How much time it will take to write out n=23 diplomas (including the first), write out this pace?
How high is the building that throws horizontal shadow 58.5 m long at angle 36°36'?
- Quarter circular
The wire that is hooked around the perimeter of quarter-circular arc has length 14π+56. Determine the radius of circle arc.
Can umbrella 75 cm long fit into a box of fruit? The box has dimensions of 390 mm and 510 mm.
Dog is tied to a chain, which is mounted in a corner of the yard. Yard has the shape of a square with a side length of 20 meters. The same long is also dogchain. Are there places in the yard where dog can't reach?
- Trio 2
Decide whether trio of numbers is the side of a right triangle: 26,24,10.
- Journey to grandma
Daniel traveled to grandma. He travel 100 km along. Halfway travel by train, one quarter by bus, one tenth by the bicycle and the rest travel by car. How many km travel km by car?
The area of trapezium is 35cm2 find its altitude if the bases are 6cm and 8cm.
Small tractor wheel with a diameter of 60 cm must be rotated 8 times to overcome some pathway. How many times must turn the big tractor wheel with a radius 60 cm to overcome the same distance?
A team of colleagues done the work in 20 days. After adding 2 colleagues from the beginning the work was completed in 15 days. How many members has the colleague team?