21. Whiten grout. 
If your tub and tile grout looks grubby, spray on peroxide, let it sit for a while and then scrub with an old toothbrush. You may have to repeat this process a few times. You also can mix hydrogen peroxide with white flour or baking soda to create a thick paste, then apply to grout and let it sit for a few hours. It will look nearly new when you rinse it off.
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