Marissa is reading over her blood work results from her doctor. According to the report, there are about 3.7 × 105 platelets and about 9,300 white blood cells in a microliter of blood.
What is the total number of platelets and white blood cells in a microliter of blood?
A.
3.8 × 105
B.
3.8 × 104
C.
4.63 × 105
D.
4.63 × 104
The total number of platelets and white blood cells in a microliter of blood can be calculated by simply adding the two values together.
3.7 × 10^5 (platelets) + 9,300 (white blood cells) = 3.7 × 10^5 + 9,300 = 370,000 + 9,300 = 379,300
Therefore, the total number of platelets and white blood cells in a microliter of blood is 3.793 × 10^5.
This is closest to option A: 3.8 × 10^5.
A pound of sugar weighs approximately 4.5 × 102 grams. If each grain of sugar weighs 6.25 × 10-4 of a gram, which is the best estimate for the number of grains of sugar in a 5-pound bag?
A.
3.6 × 108 grains
B.
3.6 × 105 grains
C.
3.6 × 107 grains
D.
3.6 × 106 grains
To find the number of grains of sugar in a 5-pound bag, we first need to convert 5 pounds to grams:
1 pound = 4.5 × 10^2 grams
5 pounds = 5 x 4.5 x 10^2 = 2.25 x 10^3 grams
Next, we will find out how many grains of sugar can be made from 2.25 × 10^3 grams of sugar:
1 grain = 6.25 × 10^-4 grams
Number of grains = 2.25 × 10^3 / (6.25 × 10^-4) = 2.25 × 10^3 / 6.25 × 10^-4 = (2.25 / 6.25) x 10^3+4 = 3600 x 10^3 = 3.6 x 10^6 grains
Therefore, the best estimate for the number of grains of sugar in a 5-pound bag is 3.6 × 10^6 grains. The closest option is D: 3.6 × 10^6 grains.
Cassie added two numbers together on her calculator for her biology homework. The calculator showed the sum as 9.62E-6. She knows she used 0.000009535 as one of the numbers. What number did she add to 0.000009535 to get 9.62E-6?
A.
8.5 × 10-6
B.
8.5 × 10-8
C.
1.8 × 10-6
D.
1.8 × 10-8
To find out what number Cassie added to 0.000009535 to get 9.62E-6, we can subtract 0.000009535 from 9.62E-6:
9.62E-6 - 0.000009535 = 9.62E-6 - 9.535E-6 = 0.082E-6 = 8.2E-7
Therefore, Cassie added 8.2E-7 to 0.000009535 to get 9.62E-6. In scientific notation, 8.2E-7 is equivalent to 8.2 × 10^-7.
The closest option to 8.2 × 10^-7 is not given, but we can convert 8.2 × 10^-7 into scientific notation by moving the decimal point to the right by 7 places, which results in 8.2 × 10^-7.
Therefore, the closest estimate from the given options is not there, but the correct number she added to get 9.62E-6 is 8.2 × 10^-7.