A train travels a total of 42 km at a constant speed of 85 km/h. How long is its journey? Give your answer in minutes and seconds, to the nearest second.

30 minutes.

Step-by-step explanation;

The train travels 85km per hour, so the train moves 85km in 60 minutes. You need to find out how many minutes it takes for the train to move 42 km. Use the rule of three to find this out, using x to represent the x amount of minutes it would take for it to travel 42km.

You can place the rule of three like this: x . Cross multiply to find out the value of x, which is  29.647, this is the amount of time it takes the train to travel 42 km. Round the number to its closest value, 30 minutes.

13

step-by-step explanation:

169-1=168

168-3=165

165-5=160

160-7=153

153-9=144

144-11=133

133-13=120

120-15=105

105-17=88

88-19=69

69-21=48

48-23=25

25-25=0

since it took 13times to completely subtract it hence its square root is 13