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# Tutor profile: Sara H.

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Sara H.
CRLA Certified Tutor and Masters Student
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## Questions

### Subject:Basic Math

TutorMe
Question:

Jordan needs to buy a computer for school. Her parents say they will pay 20% of the list cost of the laptop, but she is responsible for the rest. The computer is on sale at the office store for \$799. Jordan also clipped a 15% off coupon out of the weekly flyer. How much will she be paying out of her own pocket?

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Sara H.

The first thing we need to tackle in this question is what portion Jordan’s parents will pay for the computer. They are committing to pay 20% of the original price, not the sale price, so we multiply the full list cost of \$799 by 0.20. Remember to convert your percentages to decimal points or fractions before doing multiplication! 799 x 0.20 = 159.80 -> the money Jordan’s parents will contribute. Next, we need to determine how much the computer costs at the office store this week with the 15% off coupon. 15% is 0.15 as a decimal and we multiply that by the list price of \$799. 799 x 0.15= 119.85 -> the discount Jordan receives from the coupon. Now, it can be helpful to set up your equation to find the final answer with words before adding any numbers to make sure you find the right value asked for in the word problem. In this case, we are trying to find how much money Jordan is paying out of her own pocket for the laptop. Jordan’s out of pocket cost= Original list price – her parent’s contribution – the coupon discount Now that we know our terms, it is easy to plug in the numbers to get our final answer. \$799 - \$159.80 - \$119.85 = \$519.35 Remember to write your final answer as a complete sentence! Jordan will pay \$519.35 out of her own pocket for her new school computer.

### Subject:Psychology

TutorMe
Question:

What is the difference between a positive punishment and a positive reinforcement? How can there be positive punishment, isn’t that a contradiction?

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Sara H.

### Subject:Biology

TutorMe
Question:

What is evolution and what are its main mechanisms? Explain how one of these mechanisms contribute to evolution what is evolution and what is its main mechanisms? Explain how one of these mechanisms contribute to evolution with an example.

Inactive
Sara H.

Evolution is the change in allele frequencies in a population over time. There are two important points in this definition. First, that evolution is a change in the allele frequencies, not a change in individuals. Individuals do not evolve, simply the incidence and prevalence of certain alleles may change (remember that alleles are just variations of genes). Secondly, time. Evolution does not happen instantly, it happens over many generations of a population. The mechanisms of evolution are genetic drift, natural selection, mutation, gene flow, and non-random mating. If none of these are occurring, the population is said to be in Hardy-Weinberg equilibrium and the allele frequencies do not change, so no evolution. I will explain how a single mechanism, natural selection, may contribute to the evolution and cause a change in allele frequencies. If there is an advantage to having a certain phenotype or genotype, that is, it makes an individual more fit (more likely to pass on its genetic information through reproduction), it will change the frequency for which it will arise. If the certain allele causing the phenotype or genotype is present in these more fit individuals, they will reproduce more frequently than those without said allele, thereby increasing the allele frequency in the next population. For example, if a certain coloration makes an organism less likely to be found by predators this could be advantageous. If the tweedle beetle comes in two colors, brown and white, and they live on tree bark, which coloring do you think would be more advantageous? Of course, the brown tweedle beetles are harder for the birds to spot than their white counterparts. This means the brown beetles are more likely to live on and reproduce, thereby passing on their brown allele to their offspring. This outside force of predation and natural selection is changing the allele frequency than what would be expected without the outside force. Natural selection can work both ways, either increase or decrease an allele frequency; evolution need not be positive or negative change, just change in allele frequency over time.

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