Question

round off each of the following quantities to rwo significant figures a.25.55mL. b.0.00254. c.1.491×10^5mg d.199g​

Answer 1

Rounding off the given numbers into two significant figures.

a) 25.55 ml

• In the given number, the first two significant numbers are 25. The number followed by 5 is 5.
• Due to this reason, 5 influences 5. Thus the round off value of the given number to 2 significant figures is 26.
• Thus 25.55 ml = 26 ml.

b) 0.00254

• As per the rules for identification of significant number, the zero preceding the numbers are not considered as significant.
• Thus the first two significant numbers in the given case are 25. The number followed by 5 is four which is less than 5.

• Due to this reason, 4 doesn't influences 5. Thus the round off value of the given number to 2 significant figures is 0.0025.
• Thus 0.00254 = 0.0025.

c) $1.491\times10^5$

• The given number is in exponent form. When it is written in normal form it becomes 0.00001491

• As per the rules for identification of significant number, the zero preceding the numbers are not considered as significant.

• Thus the first two significant numbers in the given case are 14. The number followed by 4 is nine which is more than 5.

• Due to this reason, 9 influences 4. Thus the round off value of the given number to 2 significant figures is 15.
• Thus 0.00001491 = 0.000015.

d) 199g

• In the given number, the first two significant numbers are 19. The number followed by 9 is 9 which is more than 5.
• Due to this reason, 9 influences 9. Thus the round off value of the given number to 2 significant figures is 20.
• Thus 199 g = 200 g.

Learn more about such concept

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Answer 2

Answer:

1) 26 2) 0.0025 3) 1.45^5mg 4) 200g