Question

Correct any answers that have the incorrect number of significant figures.

      (a) (908.4 - 3.4) / 3.52 x 10⁴ = 0.026

      (b) (1206.7 - 0.904) x 89 = 1.07 x 10⁵

      (c) (876.90 + 98.1) / 56.998 = 17.11

      (d) (4.55 / 407859) + 1.00098 = 1.00210

Answer 1

(A) (908.4 - 3.4) / 3.52 x 10⁴ = 905.0 / 3.52 x 10⁴ = 0.026

The answer must have THREE SIGNIFICNT FIGURES. Therefore right answer is 0.0260

EXPLANATION: Remove the bracket first. After perorming ADDITION OR SUBTRACTION the answer obtained must have same no. of DECIMAL PLACES as are in the number which has LEAST NO. OF DECIMAL PLACES. That is why we wrote first

(908.4 - 3.4) / 3.52 x 10⁴ = 905.0 / 3.52 x 10⁴

Then in case of division and/or multiplication the answer MUST HAVE SAME NO. OF SIGNIFICANT FIGURES AS ARE PRESENT IN THE NUMBER THAT HAS LEAST NO. OF SIGNIFICANT FIGURES.

3.52 has least no. of significant numbers i.e; 3 significant figures . So answer must have only three significant figures.

0.026 has only 2 significant figures because zeros left to 2 are not significant. Therefore correct answer is 0.0260. As the last zero is significant.

(B) (1206.7 - 0.904) x 89 = 1.07 x 10⁵

(1206.7 - 0.904) x 89 = 1205.7 X 89 = 1.07 x 10⁵

in 1205.7 X 89 the lowest no. of Significant no.s are in 89. it has two significan figures therefore answer must have 2 significant figures only.

Correct answer is 1.0 X 10⁵

(C) (876.90 + 98.1) / 56.998 = 17.11

(876.90 + 98.1) / 56.998 = 975 / 56.998

(876.90 + 98.1) / 56.998 = 975.0 / 56.998 (as explaned above for addition and subtraction operation)

975.0 / 56.998 = 17.11 The answer is corect.

(d) (4.55 / 407859) + 1.00098 = 1.00210 ANSWER is CORRECT. As explaned above