Quantitative Aptitude - Arithmetic Ability Questions

The average of 9 observations was found to be 35. Later on, it was detected that an observation 81 was misread as 18. The correct average of the observations is

10 people can build a wall in 12 days. Six people, each only half as efficient as those in the first group, will be able to complete 3/5 of such a wall in

Robin can do a work in 10 hours. Pradeep and Robin together can do the same work in 4 hours. Pradeep and Nitin together can do the samework in 5 hours. In how many hours Nitin alone can complete the same work?

If 5+x+5-x5+x-5-x = 3,then what is the value of x ?

In an army selection process, the ratio of selected to unselected candidates was 4:1. If 90 less had applied and 20 less selected, the ratio of selected to unselected would have been 5:1. How many candidates had applied for the process?

In ΔABC, D and E are points on side AB and AC respectively. DE is parallel to BC. If lengths of AD, DB and DE are 8 cm, 6 cm and 7.2 cm respectively, find length of BC?

X can complete a task in 8 days, whereas Y can complete the same task in 10 days. If they work together, in how many days will the task be completed?

PQRS is a square whose side is 16 cm. What is the value of the side (in cm) of the largest regular octagon that can be cut from the given square?