There is 278 calories for 100g of kiri cheese, each portion of kiri cheese has 46 calories. how many kiri portions do I need to equal 50g?

One needs 3.02 portions of kiri cheese to equal 50 g

Step-by-step explanation:

If there is 278 calories for every 100 g of the cheese, then 50 g of the cheese would contain half of that amount of calories, that is: in 50 g of kiri cheese, there is 278/2 = 139 calories.

since each portion has 46 calories, then  to reach to 139 calories (which is 50 g of the cheese) one needs 139/46 = 3.02 portions

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.