Math practice for 13 year olds - page 254 of 428

Number of problems found: 8557

Diluting Alcohol to Percentage
We want to prepare 200g of 64% alcohol. We have enough 80% alcohol to dilute with water. How much 80% of alcohol and water will we need?
Catching Up on Bicycle
The mile came from point A at 13 hours at a speed of 4 km/h. At 3.30 PM, Líba rode her at a speed of 20 km/h. How many minutes will Líba catch up with Milo?
Five inlets
The tank can be filled with five equally powerful inlets. If four inlets fill the tank, it takes 30 minutes to fill one-third of the tank. How many minutes does it take to fill an empty tank if it is filled with all five inlets?
Miss competition
How many girls took part in the Miss School competition if the nines grade made up half of the contestants, two-thirds of the remaining girls were from eighth grade, and the seventh grade were three?
Cup Diameter Ball Displacement
The mug has the shape of a cylinder with a height of 60.7 mm. There is two dl of water in it. If we dip a ball with a diameter of 40 cm into the water, the water will not overflow. What is the minimum diameter of the cup?
Aquarium Water Level Area
There are 140 liters of water in a rectangular aquarium with 800 mm and 50 cm base dimensions. How high in cm does the water level reach? What is the area in dm² of the inner walls of this aquarium up to the water level?
Screens
The area of a 25-inch TV screen is 300 inch² the area of a 40-inch TV screen is 768 inch². The area of the smaller screen is what percent of the area of the larger screen?
Pupils
There are 350 girls in the school, and the other 30% of the total number of pupils are boys. How many pupils does the school have?
Number multiplication puzzle
To get their sum, what number do you have to multiply the difference between 3 1/2 and 2 3/4?
Chickens and hares
There were chickens and hares in the yard. Together they had 22 heads and 54 legs. How many hens were there in the yard?
Two Workers Digging Canal
The first worker digs a canal in 3 hours. The other will dig the trench in 4 hours. They will work 1 hour opposite each other and then together. How long will it take them?
CD DVD shelf
Juraj had music CDs and DVDs stored on the shelves. There are a total of 64. How many DVDs are on the shelf if there are seven times less than a CD?
Equation - inverse
Solve for x: 7: x = 14:1000
Bicyclist Meeting Walker
At 8:00, Peter set out on a hike at 5 km/h. At 9:12, Michal followed him on a bike at a speed of 20 km/h. At what time did Michal Petra run, and how many kilometers did he cover?
Polder filling
The polder has two tributaries. A larger inflow will fill an empty polder in 12 hours. The polder is already a quarter full. If we open both tributaries, the polder will be filled in 6 hours. How long would it take for a smaller inflow to fill an empty po
Two number sum
The sum of the two numbers is 46. It holds that two times the first is one greater than three-fifths of the second. What are the numbers?
Reminder and quotient
Numbers A = 135 and B = 315 are given. Find the smallest natural number R greater than one so that the proportions R:A, R:B are with the remainder 1.
Car crash
After a traffic accident, police measured 1.16 permille of alcohol in the driver's blood. About 5 kg of blood circulates in the human body. What amount of alcohol did the driver have in the blood?
Circular arc length
The length of the circular arc at the corresponding angle of 120 ° is 8 cm. What is the size of the whole circle? What is its radius?
Workshops
The first workshop will complete the robot itself in 15 days, and the second workshop in 10 days. They started together, but only the second workshop worked after three days. Thus, the work will take 15 days.

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