Standard Index Form

(3.1 × 108) is in standard index form.

(12.999 × 109) is not represented in standard index form because it standard form is 1.29 x 10¹⁰

To write 5600 in standard index form, move the decimal point so there's one non-zero digit before it. 5600 = 5.6 × 1000 = 5.6 × 10^3. You moved the decimal 3 places left, so the exponent is 3.

32000 = 3.2 × 10000 = 3.2 × 10^4. The decimal point moved 4 places to the left (from after the last zero to between 3 and 2), giving exponent 4.

1.5 × 10^-4 means 1.5 divided by 10^4 = 1.5 ÷ 10000 = 0.00015. The negative exponent tells you to move the decimal point 4 places to the left.

0.0001234 = 1.234 × 0.0001 = 1.234 × 10^-4. To get one non-zero digit before the decimal, move it 4 places right (from 0.0001234 to 1.234), giving exponent -4.

15 million = 15,000,000 = 1.5 × 10,000,000 = 1.5 × 10^7. The decimal moves 7 places left to put one digit before it.

Combined population = 123.6 + 89.4 = 213 million = 213,000,000 = 2.13 × 10^8. Add the millions first, then convert to standard form by moving decimal 8 places left.

Total budget = 89.3 + 126.4 + 67.9 = 283.6 billion = 283,600,000,000 = 2.836 × 10^11. A billion is 10^9, so 283.6 billion = 283.6 × 10^9 = 2.836 × 10^11.

Combined area = 182,234 + 881,776 = 1,064,010 km^2 = 1.064010 × 10^6 km^2. Add both areas precisely, then express in standard form by moving decimal 6 places left.