Mum spent 2/3 of her money and put 1/4 of the remainder in the bank. she put $20 in the bank. how much did she start with?

Let x be the initial amount of money. We know that mum spent 2/3 of this amount, so she's left with

Of this remainder, only 1/4 was deposited, which is

And this amount equals 20, so we have

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.

27

step-by-step explanation: