# Percentages + time - math problems

#### Number of problems found: 81 How large must the group of people be so that the probability that two people have a birthday on the same day of the year is greater than 90%?
• Population The town has 65,000 inhabitants. 40 years ago, there were 157,000. How many people will live in a city in 10 years if the population's average rate is as in previous years?
• Growth of wood The annual growth of wood in the forest is estimated at 2%. In how many years will make the forest volume double?
• Slow saving in banks How long will it take to save € 9,000 by depositing € 200 at the beginning of each year at 2% interest?
• Bulbs The probability that the bulb can operate 4000 hours is 0.3. What is the probability that exactly one of eight bulbs can operate 4000 hours?
• 15 teachers 15 teachers teach for a combined amount of 128 days over a period of 64 days. What is this expressed as a percentage?
• Server Calculate how many average minutes a year is a webserver is unavailable, the availability is 99.99%.
• Deposit is pesos Sally deposits Php.22,000 in her savings account. If the bank pays 1.5% interest per year, how much will she receive at the end of the year?
• Millionaire Mr. Smith have gone withdraw from bank saving interest € 1,500. How big was his initial deposit if the annual interest rate is 1.5%? After two hours and 40 minutes the job is finished. Compared to last year we were 40 minutes faster. What is the percentage increase to our performance?
• Interest p.a. Calculate the value of interest in period of 1 year from the deposit 62000 CZK at 8 percent interest rate, after deducting 15 percent tax.
• Electric cooker During which time t does an electric cooker with power input P = 500 W and with efficiency n = 75% heat water with mass m = 2 kg and temperature t1 = 10°C to the boiling point (t2 = 100°C). The specific heat capacity of water is c = 4 180 J. Kg-1. K-1
• Price inflation This year the average wage grew by 4.5%. Prices rose by 2%. How much did the real wage increase in the given year?
• A trip to the peak Dry Calculate what percentage is rising trip from Strečno to peak Suchý (Dry peak) longer than the descent back. Team trio of tourists (Palo, Peter and Andrew) rise took 4:21 and descent 3:08.
• TV fail The TV has after 10,000 hours average 35 failures. Determine the probability of TV failure after 400 hours of operation.
• Christmas Calculate how much of the school year (202 days long) take Christmas holidays 19 days long. Expressed as a decimal number and as a percentage.
• Loan 4 Mr santos borrowed Php.18,000 at 1.5% interest for one year. What was the total amount he paid for the end of the 1-year term?
• Simple interest 4 Find the simple interest if 5243 USD at 4.3% for 261 days. Assume a 361-day year.
• Interst on savings The bank offers 1.6% interest. How many euros have to insert at the beginning if we received € 15 on the interest?
• Crystal The crystal grows every month 1.2 permille of its mass. For how many months to grow a crystal from weight 177 g to 384 g?

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