Math practice for 13 year olds - page 79 of 435
Number of problems found: 8682
- Observations 81124
The number of observations is 24, and the value of the mean is 28, then the sum of all the values is ... - Revolutions 81118
1. A disc makes 15 revolutions per minute. Determine his angular speed and the boy's speed on the seat that describes a circle with a radius of 5 m. 2. The grinding wheel rotates at 600 revolutions per minute. Determine the period and angular velocity. Th - Probability 81117
Martin forgot the 4-digit PIN, and he remembered the first three numbers. The fourth number is odd. What is the probability in % that he will be able to determine the PIN? He has only one attempt. - Twenty-five 81116
Twenty-five pencils were bought as prizes in the school competition. The more expensive pencils were for 20 CZK, the cheaper ones for 15 CZK. The entire amount paid was 455 CZK. How many are there? - Chocolate 81103
I paid 36 crowns for butter and chocolate. Butter was CZK 6 more expensive than chocolate. How much did the chocolate cost? - Painters 81101
Four painters painted the house in 14 days. How long will it take if 2 more come to help after 5 days? - Dimensions 81100
The area of the rectangle is 81.25 cm². If we increase its length by 5 mm, its area increases by 4%. Determine its dimensions.
- Reduced 81099
A square has a side length of 25 cm. How big is its area if the side is reduced by 25%? - Quadrilateral 81097
The quadrilateral ABCD is symmetrical about the diagonal AC. The length of AC is 12 cm, the length of BC is 6 cm, and the interior angle at vertex B is right. points E and F are given on the sides AB, and AD so that the triangle ECF is equilateral. Determ - Circumference of edges
The hexagon pyramid has a circumference of 120 cm, and the length of the side edge is 25 cm. Calculate its volume. - Unknown 81081
The number 420 is 20% more than the unknown number. What is the unknown number? - Numbers 81079 The ratio of the two numbers is 1:3. Half of the larger one is 135. What is the sum of the two numbers?
- Part-time 81067
I had 350 euros left over from the money I earned from the part-time job. I bought soccer cleats with half of the money I earned and a soccer ball with the other half. How much did I earn from the part-time job? - Advantageous: 81060
Determine which purchase is more advantageous: ... ... - Participants 81059
Participants paid out 3,300 euros in 40 banknotes. Some were 50e, and others were 100e. How many were there?
- Tourists 81058
Tourists traveled by bus to Croatia. They drove the highway in 8 hours at an average speed of 100 km/h. How fast would they cover it if they walked at an average speed of 120 km/h? - Corresponds 81049
Cyril marked a square plot of land on a map with a scale of 1 ∶ 50,000 and calculated that its side corresponds to 1 km. He reduced the map on the copier so that the marked square had an area smaller by 1.44 cm² than on the original map. What was the scal - Younger Carlos
In 2005, Peter was three times as old as Carlos. In 2020, Carlos was half his age younger than Peter. In which year was Peter born and in which Carlos? - Together 81046
Two painters are painting the factory fence together. If everyone worked alone, the first would finish the job in 16 days, the second in 20 days. When will they finish the work together? - Apricots 81045
We paid a total of 85 crowns for the purchase of 2.5 kg of apricots and 1.5 kg of peaches. A kilogram of peaches is CZK 2 cheaper than a kilogram of apricots. How much CZK was paid for the apricots?
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