Math practice for 13 year olds - page 330 of 424

Number of problems found: 8463

Unknown 3922
16% of the unknown number equals the square root of the number 25. Find this unknown number.
Circumference 3919
Determine the diagonal of a square whose circumference is equal to 72 cm.
Average speed
What is the average speed you have to move around the world in 80 days? (Path along the equator, round to km/h).
Area and percents
Find what percentage is a smaller cube surface when the wall's surface area decreases by 25%.
Four-digit 3912
Create all four-digit numbers from digits 1,2,3,4,5, which can repeat. How many are there?
Cuboid enlargement
By how many percent increases the volume of the cuboid if every dimension increases by 30%?
Pet store
They sold fish from one aquarium from the breeding product (Zverimex). Ondrej wanted half of all the fish, but to avoid cutting any fish, he got half the fish more than he wanted. Matej wanted half of the remaining fish, but like Ondrej, he got half the f
Three friends
Three friends divided the profit by 104,650 CZK so that for every 4 CZK, which got the first friend, equals five crowns for the second, and for every 9 CZK, which got the second, equals 16 CZK for the third. Question: Who got the most and how much?
Cacao
Cacao contains 34% filling. How many grams of fill are in 130 g cacao?
Unknown number 7
16% of the unknown number is 21 less than the unknown number itself. Determine the unknown natural number.
Three children
Three children eat eight chocolates in 6 days. How many chocolates do six children eat in 18 days?
Percentage 3892
The bar contains 81g of coconut per 200g. What percentage of coconut does the bar have?
Probability 3891
Michal chose blue, white, red, orange, black, and brown shorts. What is the probability that he will select blue shorts?
Expression 3887
Determine what z equals in the expression 169^z = 2 · 6.5
Chocolate 3886
Chocolate has 86% cocoa. Determine how many grams of cocoa are in 165-gram chocolate.
Determine 3885
Determine the sum of the square roots of 81.
Determine 3880
Determine how much equals 16% of a) 32, b) 44, c) 34, d) 25
Runner 2
Marian runs 12 meters in 8 seconds. How far would Marian run for 70 seconds if he still runs at the same pace?
Independently 3874
Josef would do the work himself in 5 hours. Josef and Michal would do the work together in 3.5 hours. Determine how long it would take Michal to do the job independently.
Determine 3873
Determine the ratio of the square root of the number 27 and the square root of the number 16.

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