24000 blood donors were registered with a charitable hospital. The number of donors increased at the rate of 5% every six month. Find the time period at the end of which the total number of blood donors becomes 27783.

6400 workers were employed to construct a factory in 4 years. A the end of the first year, 25% workers were retrenched. At the end of the second year, 25% of those working at that time were again retrenched. However, to complete the project in time, the number of workers was increased by 25% of the total number of workers left at the end of third year. How many workers were working during the fourth year ?

The number of square units, A, in the area covered by a bacteria culture is increasing at a rate of 20% every 7 days. If the bacteria culture initially covers an area of 10 square centimeters, which equation can be used to find the number of square units in the area covered by the bacteria culture after d days?

Five coins were simultaneously tossed 1000 times and at each toss the number of heads were observed. The number of tosses during which 0, 1, 2, 3, 4 and 5 heads were obtained are shown in the table below. Find the mean number of heads per toss. No. of heads per toss No. of tosses 0 38 1 144 2 342 3 287 4 164 5 25 Total 1000

Three colonies of insects were each treated with a different pesticide over an 8-week period to test the effectiveness of the three pesticides. Colonies A, B, and C were treated with Pesticides A, B, and C, respectively. Each pesticide was applied every 2 weeks to one of the three colonies over the 8-week period. The bar graph above shows the insect counts for each of the three colonies 0, 2, 4, 6, and 8 weeks after the initial treatment. Of the following, which is closest to the ratio of the total number of insects in all three colonies in week 8 to the total number of insects at the time of initial treatment?

The given bar graph shows the number of identical articles sold by 5 different stores A, B, C, D and E during a particular month. Study the bar graph and answer the following questions : (i) Which store sold the largest number of articles ? (ii) By what per cent is the sale of store D more than that of store B ? (iii) Find the ratio of the total sale of the two highest selling stores to the total sale of the two least selling stores. (iv) By how much must store E increase its sale to catch up with its nearest rival store ?