The teacher will use 3 rolls only to have perfect measurements.
1 yard = 3 feet
4 large bulletin boards are there each needing 9 yards of border.
That means 4 large bulletin boards in total need
9×4 yards of border
= 36 yards of border
= 108 feet of border
Also, there is a small bulletin board that only needs 12 feet border
Hence, in total there is a need for
108 + 12 = 120 feet border.
The border is sold in 40-foot rolls.
Hence, there is a need for 120/40 rolls
i.e. 3 rolls
Hence, the teacher will use 3 rolls only.
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Answer:
40 hours
Step-by-step explanation:
500 ÷ 12.5 = 40
A petri dish is simply a circle; thus, we use the formula of the area of the circle which is <span>πr^2.
Given r = 40 mm
A = </span>π(40)^2 = <span>5026.55 sq. mm
</span>
Population density = bacteria count / area
PD = 2,100 / <span>5026.55
PD = </span><span>0.417782 bacteria / mm sq.
Therefore, the answer is approximately 0.418 </span><span>bacteria per square millimeter.</span>
