ILC MATH Olympiad Teacher Lefyn Concept Prime number

ILC MATH Olympiad Teacher: Lefyn

Concept ● Prime number ● Fraction ● Geometry

Prime number A prime number (or a prime) is a natural number greater than 1 that is not a product of two smaller natural numbers. A natural number greater than 1 that is not prime is called a composite number. For example, 5 is prime because the only ways of writing it as a product, 1 × 5 or 5 × 1, involve 5 itself. However, 4 is composite because it is a product (2 × 2) in which both numbers are smaller than 4.

Fraction ● ● ● Numerator Denominator Division: numerator divide by denominator Equivalent fraction ½ = ? /8

Geometry ● Perimeter ○ Perimeter is the distance around a two-dimensional shape ● Rectangle area ○ ○ LXW angle ● Square ○ ○ Four equal sides Angle ● Triangle ○ ○ Altitude: a line perpendicular to the base Area: h b/2 ● Circle ○ ○ Diameter = 2 r Circumference = 2Πr = Πd

#1 We know that A=length x width 20 = 5 x ? ? =4 One side is 5 The other side is 4 5 x 2 + 4 x 2 = 18

#2 6 + 10 = 16 is the total # of marbles Because he lost half of his marbles, so we need to divide 16 by 2 M = 16 / 2

#3 280 x 10 = 2800 2 x 280 = 560 + 2800 = 3360 C is correct

#4

#5 We assume that all of the animals are chickens 4 x 2=8 There are 12 legs 12 - 8 = 4 4 / 2 = 2 (the # of cows) 4 - 2 = 2 (# of chickens)

#6 Triangle area formula A=bxhx½ Square A = side x side Square 5 x 5 = 25 We get that the area for the square is 25, triangle has the same area as the square 25 = 10 x h x ½ 10 h = 50 H=5

#7 (1+2+3+4) x 1985 = 10 x 1985

#8 The answer is D because a prime number has only the factors of one and itself. If two prime numbers are multiplied together then the product has at least 4 factors so it isn’t prime.

#9 There are 20 nine in there So 20 x 9 = 180

#10 x + 3 = 2 x 3=x

#11 300 x 2 + 150 = 750 (148 + 152 = 300), (149 + 151 = 300)

#12 2 r = d 8 x 2 = 16

#13 Equilateral triangle has 3 equal sides 24 / 3 = 8

#14 7 x 5 = 35 (there are 35 days in a month) 35 x 15 = 525

#15 6 x 30 = 180 There are six sides in a hexagon

#16 Dee is the tallest because Ann is 2 cem shorter than Bob, and Bob is 1 cm shorter than Carl which means Carl is 3 cm taller than Ann. Bee is 4 cem taller than Ann. So Dee is the tallest

#17

#18 Set x = the # of kid tickets y = the # of adult tickets x+ y = 13 2 x + 3 y = 29 2 x + 2 y = 26 2 x + 3 y = 29 y=3 x = 10

#19

#20 3 -2=1

#21 4 / 2 = 2 (width) (2+4) x 2 = 12

#22 51 / 24 = 2. . . 3 (two days + 3 hours) August 15 th + 2 days = August 17 th 10: 00 P. M. + 3 hours = 1: 00 A. M. The answer is August 18 th because after 12: 00 A. M. , a new day starts

#23 One dozen eggs = 12 eggs 50% = 0. 5 12 x 0. 5 = 6

#24 1 hour = 60 mins 60 / 20 = 3 8 x 3 = 24

#25 Because it is a square, so all four sides are equal. 4 x 3 = 12

See you next week! Have a good weekend!!!