Hooray! It's lesson 35!

Percent

100

What percent of the first 20 natural numbers are one-digit numbers?

45%

200

Find the number if 6% of it is 20% of 6.

20

300

If a=12 and 120% of a is equal to 80% of b, then what is a+b ?

30

400

if 80% of M is equal to 50% of N, and N is not 0, what is M/N equal to?

1.6

500

What percent of the first 20 natural numbers are prime one-digit numbers?

20%

Mental Calculation

100

(56x63x11x15)/(55x21x16x18)

7/4 or 1.75

200

(1-1/2)(1-1/3)(1-1/4)....(1-1/99)(1-1/100)

0.01 or 1/100

300

81+82+...+99+100

1810

400

1/(1*2)+1/(2*3)+1/(3*4)+1/(4*5)+...+1/(29*30)

29/30

500

(1+2/3)(1+2/5)(1+2/7)(1+2/9)...(1+2/n)(1+2/(n+2))

(n+4)/3

Equations

100

92+56/(14-x)=100

x=7

200

(x+8)/2-3=(x+8)/4

x=4

300

2024/2025 *(2x-3)-2023/2024*(2x-3)=0

x=1.5

400

|x+8|=-|x+8|

x=-8

500

(x-3)/5=x-3

x=3

SAT

100

If a/b =2, what is the value of 4b/a

2

200

If 5x+6=10, what is the value of 10x+3?

11

300

For what value of n is |n-1|+1 equal to 0?

There is no such value for n

400

If 5/x =15/(x+20), what is the value of x/5?

2

500

Find (2/5) % of 2000.

8

Out of the Box

100

If the sum of 4 consecutive numbers is 1998, what is the 3rd number?

500

200

xy=4747 and x-y=54. What is x and y?

x=101, y=47

300

Find 2 ways to write 11/12 as a sum of three unit fractions.

11/12=1/2+1/3+1/12 or

11/12=1/2+1/4+1/6

400

54*12*3*1*11=20. Replace * with +,-,x,/. You can use () if needed.

54-12-(3-1)x11=20

500

If the length of the rectangle increased by 20% and its width increased by 50%,  then the area is increased by...?

...by 80%