Prime numbers - practice for 13 year olds - page 2 of 9
Number of problems found: 165
- Together 81979
Three friends split the reward in the ratio of 3:5:7. One of them received exactly €49. How many euros did they get together? - Probability 81964
Calculate the probability of the event that you sit in seats 1 to 30 in the cinema at: a) seat marked with a prime number b) seat marked with an even number c) a seat marked with a number divisible by 3 or 4 - Calculate 81492
Jirka went on a moped for a three-day trip. He drove 90 km on the first day, 30 km on the second day, and 60 km on the third day. He always drove at the same average speed and always the whole number of hours. Calculate the average speed if Jirka drove at - The grocery
Susan has decided to make grocery combos for her shop. The wholesaler she buys from sells sugar in packets of 20 in a carton, flour in packets of 12 a carton, and 15 bags of rice in a carton. How many of each item should she buy so there are an equal numb
- Greatest common factor
What is the GCF of 8 and 20? - Two numbers sum and product
Two numbers have a sum of 12 and a product of 27. What is the larger number? - Rectangle-shaped 80074
Pupils had to stack rectangle-shaped pictures with dimensions of 210mm and 84mm so as to cover the square. What is the smallest square we can cover like this, and how many images do we need? - Reduce ratio
Express the following ratio in simplest form: 30:42 - Divisible 79464
The teacher wrote a number less than 50,000 on the board. The first student said: This number is divisible by 2 The second student said: This number is divisible by 3 And so on, down to the last one who claimed it was divisible by 13. Two in a row lied. W
- Owl A,B,C
Owl a gives a hoot every 7 minutes. Owl b gives a hoot every 9 minutes. Owl c gives a hoot every 5 minutes except when he has heard owl a or b give a hoot within the previous 2.5 minutes. If this happens, owl c doesn't give a hoot. If all three owls give - Three 205
Three metallic bars of lengths 400 cm, 600 cm, and 720 cm are cut into equal pieces. Find the largest possible area of a square that can be made from any of the three bars. - Susan 3
Susan has 90 sweets, 36 chocolates, and 60 jellies. She wants to pack the items equally into goodie bags without any leftover items. How many bags will she pack maximum? How many sweets, chocolates, and jellies will be in one bag? - Treasury 73334
Peter has only two crowns in the treasury and can divide them both in a ratio of 4:5 and in a ratio of 4:7. How many crowns does Peter have in the money box if the amount saved is less than 300 CZK? - Divisible 72004
Find the natural number between the numbers 70 and 80 divisible without the remainder 5, 3, 15, and 25.
- Rectangles 70304
How many rectangles with side lengths expressed in natural numbers have an area of 96 cm²? - Lengths 69314
We must cut three steel bars with 24 dm, 3 m, and 160 cm lengths into equal lengths. Find their maximum length and number. - Probability 65464
We randomly draw one out of 18 cards with numbers from 1 to 18. What is the probability that the ticket drawn is a prime number? Write the result as a decimal number rounded to two decimal places. - Percentages 64334
In the first delivery of 120 parts, there was 5% waste. In the second delivery in which, 10% of the 80 were scrapped. How much scrap was brought in with the first and second deliveries combined? What % of scrap was there in both deliveries of parts, out o - Increased 64324
The number of books in the city library increased by 0.2% in 2008 and 0.6% in 2009. At the same time, the total number of books remained less than 300,000. How many books were added to the city library in 2009?
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