Math practice for 13 year olds - page 416 of 422
Number of problems found: 8426
- 3-bracket 3
Two angles in a triangle are 90° and 45°. Has the triangle at least two equal sides? - Number
Is number 2.8814789 irrational? - Ratio
Increase the number 25.6 in the ratio 7:4. - Chord
In a circle with a radius r=60 cm is the chord, 4× longer than its distance from the center. What is the length of the chord? - Box
Calculate the angle between box base 5 x 10 and body diagonal length 13. - Rotating cone II
Calculate the area of the surface of a rotating cone with base radius r=15 cm and height h=13 cm. - Is right?
Is a triangle with sides 15, 66, and 68 right triangle? - Proof I
When added to the product of two consecutive integers larger one, we get the square larger one. Is this true or not? - Energy saving
They released three different independent inventions saving 15%, 17%, and 16% energy. Some considered that with the use of these inventions, the total savings would be 15% + 17% + 16% = 48%. Is this true? How much will the percent of energy save all three - Bulbs
In the box are 16 bulbs with power 75 W, 14 bulbs with power 40 W, and 10 with 50 W. Calculate the probability that a randomly selected bulb is: a) 40 W b) 75 W or 40 W - Kitchen
The kitchen roller has a diameter of 78 mm and a width of 315 mm. How many square millimeters roll on one turn? - Gear wheels
Two gear wheels, which fit together, have the number of teeth z1=43 and z2=154. Calculate the speed of the first wheel if the second wheel rotates 766 revolutions per minute. - Median
In the right triangle are sides a=96 dm b=31 dm. Calculate the length of the medians tc to the hypotenuse. - Rectangles
How many rectangles with area 8855 cm² whose sides are natural numbers? - Secret number
Find the secret number n, which reversed decreases by 15.4 if the number increases by 15.4. - Seedcake
Seedcake costs 20 cents. How many minimum seedcakes must we buy that we can pay in cash, only whole euros? - Conserving water
Calculate how many euros are spent annually on unnecessary domestic hot water, which cools during the night in the pipeline. The residential house has 223 m of hot water pipelines 1" and the hot water has a price of 14.6 Eur/m³. - Triangle
Calculate the triangle's heights ABC if the triangle's sides are a=26, b=81, and c=73. - Diamond
Find the side of the diamond if its area is S = 194 cm² and one diagonal u2 = 44 cm. - Lead cube
Calculate the cube's edge made from lead, which weighs 14 kg. The density of lead is 11341 kg/m³.
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