If i had a granade as my weapon and a tank as my target, i would seriously consider running away. admitedly, you can disable a tank with a granade, but that dose not happen much.
As to the RPG 7, , its original penetration capability was around 320mm of steel. The modern MBTs have the equivilent of around 500-1000 mm of steel, depending on the area of the tank. there arehowever two exeptions:
-Most of these MBTs have spots that are much thiner and if those are hit the RPG wll penetrate.
-There are new RPG warheads, that were made to penetrate modern armor...The include bigger shaped charges, tendom shaped charges(to deal with reactive armor and so called "cages") and so on....