An element with mass of 630 grams decays by 18.8% per minute. how much of the element is remaining after 7 minutes.

146.63 grams.

Step-by-step explanation:

The mass percent that remains after every minute is 100%-18.8 = 81.2% of the initial mass. This means after 1 minute the mass remaining is

After 2 minutes, the mass reaming is

After 3 minutes

so we see the general pattern: the grams remaining after minutes are

Now after 7 minutes the grams remaining are

146.63 grams.

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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