Math practice for 13 year olds - page 353 of 428
Number of problems found: 8549
- Messenger chase
One messenger went 7 miles every day. When he had gone 64 miles, his master sent another messenger after him, who went 9 miles daily. How many days did the second messenger catch up with the first messenger? - Costume
Denisa is preparing for a goldsmith's costume carnival. During the preparations, she thought she would let her hair wipe instead - she would apply a 5 μm thick layer of gold to each hair. How much gold would Denisa need? Assume that all hundred thousand D - Hydrochloric acid
Determine the concentration of which must have a solution of hydrochloric acid that mixes 10 l of the solution with 8 liters of 26% solution to get the solution with a concentration of 50%. - Acid solution
By adding 250 grams of a 96% sulfuric acid solution to its 3% solution, we changed its initial concentration to 25%. How many grams of 3% of the acid were used for dilution? - Water mixing - tub
The tank has water with a volume of 300 liters and a temperature of 10 °C. Add water at a temperature of 90 °C until a temperature of 30 °C is reached. How many liters of warmer water do I need to add? - Concrete block
Determine the volume of the concrete block whose one edge of the base is 3 meters long, the body diagonal is 13 meters, and the height is 12 meters. - Distilled water
Seawater contains 5% salt. How much distilled water should be poured into 40 kg of seawater so that the salt content is 2%? How many kilograms of 2% of seawater do we get? - Number difference
The difference between the two numbers is 4/3. If you know that the first number is 50% larger than the second number, specify both numbers. - Water temperatures To 25 liters of water at 50 °C, we add 15 liters of water at a different temperature. How many °C should the water be colder than 50 °C so that 40 liters of the water obtained has a temperature of 42.5 °C?
- Acid solution concentration
Calculate the concentration of the solution prepared from 6 kg of 95% sulfuric acid solution and 24 kilograms of 10% sulfuric acid solution. - Formic acid mixture
How many liters of 60% and 80% formic acid do we have to mix to get 80 liters of this acid with a concentration of 65%? - Candy
The price for 1kg of more expensive candy is 125 CZK. The price for 1kg of cheaper candy is 100 CZK. We make two different blends of candy. And now. The second blend contains 2 kilograms of more expensive candy and several kg of cheaper candy. The price p - Solution dilution
1.5 kg of a 20% NaCl solution should be diluted to a 10% solution with water. How much water will we need, and how many kilograms of diluted solution will we get? - Alcohol mixing
How many liters of 80% alcohol need to be mixed with 4 liters of 40% alcohol to get 70% alcohol? How many liters of 70% solution do we get? - Two numbers sum
The sum of the two numbers is 52.5. The first number makes up 75% of the second number. Specify both numbers. - Solution
What amount of 80% solution and water is needed to mix to obtain two liters of 60% solution of this mixture? - Parallelogram sides
In the parallelogram ABCD, the side AB is three times longer than the side BC. The circumference of the parallelogram is 20 cm. Find the lengths of the sides of the parallelogram. - Savings distribution
Milan has 84 euros. He gave his brother 20% of his savings and his sister 25%. Find how much money each has. - Two-digit numbers
How many two-digit numbers can you create from the digits 7,0,1 and 5 if the numerals can be repeated? - Mr. John
Mr. John wants to buy winter apples Spartan. There are two ways to buy: 1) buy apples at the marketplace, where 1 kg costs 15 CZK. 2) Bring the car to the agricultural farm, where the apples are sold for 9 CZK per kilogram. However, he must pay CZK 150 fo
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