Một lớp có 10% học sinh giỏi Toán, 30% học sinh giỏi Văn, 8% giỏi cả 2 môn Toán và Văn. Tìm tỷ lệ học sinh giỏi ít nhất một môn nói trên?

i used to know how to do this in 7th but i forget easily

step-by-step explanation:

the largest number of the four options is 1.8 x 10-2

you have it in scientific notation.

1.80 x 10-6   = 0.00000180

1.80 x 10-4   = 0.000180 (bigger, or "less small", than the former one)

so

1.8 x 10-2       = 0.0180. as you see. the "less small", or the biggest one of them all.

as you have negative exponent, it means you are dividing 1.8 by 100 (i.e. moving the dot towards left, two times).

if you had positive exponent for the scientific notation, power of tenths, you would be multiplying times 100 (moving the dot towards right) as below:

1.8 x (10)2 = 180

so. if you have negative exponent in scientific notation, move the dot toward left. if it is positive, toward right as many times the exponent tells you.

3

step-by-step explanation: