The density of hydrogen is approximately 9 × 10-5 , while the density of helium is approximately 2 × 10-4 . which of the following is true? a. the density of hydrogen is approximately 20 times the density of helium. b. the density of helium is approximately 20 times the density of hydrogen. c. the density of hydrogen is approximately 2 times the density of helium. d. the density of helium is approximately 2 times the density of hydrogen.

Option D.

Step-by-step explanation:

Density of Hydrogen =

Density of Helium =

Now ratio of the densities =

=

= 0.22×

= 2.2

Density of Helium = 2× Density of Hydrogen

Therefore, density of Helium is approximately 2 times the density of Hydrogen.

Option D is the answer.

d) 30 units^2

area of rectangle = l × b

we know,

length = 10 unit

breadth = 3 unit

applying the formula,

= l × b

= 10 × 3

= 30 unit^2

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the inequality is:

250c+180g≥950

step-by-step explanation:

let c denotes the number of days in a week   miyoko worked as a cryptographer.

and g denotes the number of days in a week she works as a geologist.

now we are given that she earns $250 for every day she works as a cryptographer,and earns $180 for every day she works as a geologist.

now miyoko's goal is to earn more than $950 this week.

hence, the inequality could be represented as:

250c+180g≥950