In the ayaat of the noble Quran, sometimes east and west mentioned as singular like ayat 115 of Sura e Baqara:

وَلِلّهِ الْمَشْرِقُ وَالْمَغْرِبُ
2:115

And to Allah belongs the east and the west.

And at times it is stated as dual similarly as it is revealed in the ayat 17 of Rahman:

رَبُّ الْمَشْرِقَيْنِ وَرَبُّ الْمَغْرِبَيْنِ)

55:17

[He is] Lord of the two sunrises and Lord of the two sunsets.

And sometimes in the form of plural as it is mentioned in the ayat under discussion of Sura al Maarij.

بِرَبِّ الْمَشَارِقِ وَالْمَغَارِبِ

Some of the narrow minded people explain them as these terms oppose each other, whereas all of them are harmonious and each of them indicating a point. Defining that every day the sun rises from a new peak and sets into a fresh end. Therefore according to the number of days in the year we have the east and the west.

From other side in between so many east and west only two east and two wests are distinguished. One in the beginning of the summer that means the maximum height of the sun in the northern orbit another in the winter that is minimum down cast of the sun in the southern orbit. Apart from this there are other two easts and wests, they are called moderate east and west. (In the first of spring season and first of the autumn season when the day and night in the entire world is equal). The above mentioned different terms each of them have its own point and bring the attention of the man towards various changes in the sunset and sunrise in the systematic orbits around the sun.

فَذَرْهُمْ يَخُوضُوا وَيَلْعَبُوا حَتَّى يُلَاقُوا يَوْمَهُمُ الَّذِي يُوعَدُونَ)
70:42

So leave them to plunge in vain talk and play about, until they meet their Day which they are promised.

يَوْمَ يَخْرُجُونَ مِنَ الْأَجْدَاثِ سِرَاعًا كَأَنَّهُمْ إِلَى نُصُبٍ يُوفِضُونَ)
70:43

The Day when they will come out of the graves quickly as racing toward an erected idol.

خَاشِعَةً أَبْصَارُهُمْ تَرْهَقُهُمْ ذِلَّةٌ ذَلِكَ الْيَوْمُ الَّذِي كَانُوا يُوعَدُونَ)
70:44

With their eyes lowered in fear and humility, disgrace covering them (all over)! That is the Day which they were promised!

As if they are running towards their idols

These are the last ayaat of the Sura al Maarij as a warning and prediction to the obstinate, adamant and scornful unbelievers and said: Leave them on their own to sink in their vain desires and get engaged in their amusements till they meet the Day of Judgment.

فَذَرْهُمْ يَخُوضُوا وَيَلْعَبُوا حَتَّى يُلَاقُوا يَوْمَهُمُ الَّذِي يُوعَدُونَ

(70:42

They do not need the preaching more than this interpretation. They do not understand the logic and the reasons and they are never prepared to get wide awake. Let them plunge in their useless false rumors as the children who are active in their playing, till the promised resurrection day reaches them. Then they will sight everything with their own eyes.

Then to introduce that promised event, defined the signs of that horrific and dreadful day and said: The day when they come out from the graves in haste as if they are running toward their idols.

يَوْمَ يَخْرُجُونَ مِنَ الْأَجْدَاثِ سِرَاعًا كَأَنَّهُمْ إِلَى نُصُبٍ يُوفِضُونَ

(70:43

What a strange Interpretation. Their condition on the day of resurrection when they move swiftly towards the divine court of justice, it is compared to the floods of the people on the day of festival or the occasion of mourning running towards their idols. But there is a lot of difference between these two occasions. In fact this hopeless belief is ridiculing which they were boasting in their worldly life.

أَجْدَاثِ is the plural of جدث that means the grave.

سِرَاعًا is the plural of the سريع means the thing or person which is moving swiftly.

نُصُبٍ is the plural of نصيب it is a thing which is erected in place and the idols of stones installed and worshiped them, sacrificing for it and the blood of the sacrifice was pouring on them. Sanam is an idol which has a specific face and figure but the نُصُبٍ are the idols without any face, they are only in the form of the stone, worshiping them for some reason as it is said in the ayat 3 of Maideh Like the unlawful haram meat of the animal which is sacrificed before these idols.